TOR(1) Manual Page

Display a short help message and exit.

Specify a new configuration file to contain further Tor configuration options, or pass - to make Tor read its configuration from standard input. (Default: /etc/tor/torrc, or $HOME/.torrc if that file is not found.)

Allow the configuration file specified by -f to be missing, if the defaults-torrc file (see below) is accessible.

Specify a file in which to find default values for Tor options. The contents of this file are overridden by those in the regular configuration file, and by those on the command line. (Default: /etc/tor/torrc-defaults.)

Specify that Tor should treat a missing torrc file as though it were empty. Ordinarily, Tor does this for missing default torrc files, but not for those specified on the command line.

Generate a hashed password for control port access.

Generate your keys and output your nickname and fingerprint. Optionally, you can specify the key type as rsa (default) or ed25519.

Verify whether the configuration file is valid.

Write a list of Tor’s configured options to standard output. When the short flag is selected, only write the options that are different from their default values. When full is selected, write every option.

Install an instance of Tor as a Windows service, with the provided command-line options. Current instructions can be found at https://www.torproject.org/docs/faq#NTService

Remove, start, or stop a configured Tor Windows service.

Used internally to implement a Windows service.

List all valid options.

List all valid options that are scheduled to become obsolete in a future version. (This is a warning, not a promise.)

List whether each optional module has been compiled into Tor. (Any module not listed is not optional in this version of Tor.)

Display Tor version and exit. The output is a single line of the format "Tor version [version number]." (The version number format is as specified in version-spec.txt.)

Override the default console logging behavior. By default, Tor starts out logging messages at level "notice" and higher to the console. It stops doing so after it parses its configuration, if the configuration tells it to log anywhere else. These options override the default console logging behavior. Use the --hush option if you want Tor to log only warnings and errors to the console, or use the --quiet option if you want Tor not to log to the console at all.

Running tor --keygen creates a new ed25519 master identity key for a relay, or only a fresh temporary signing key and certificate, if you already have a master key. Optionally, you can encrypt the master identity key with a passphrase. When Tor asks you for a passphrase and you don’t want to encrypt the master key, just don’t enter any passphrase when asked.

Use the --newpass option with --keygen only when you need to add, change, or remove a passphrase on an existing ed25519 master identity key. You will be prompted for the old passphrase (if any), and the new passphrase (if any).

Generate a new family ID key in basename.secret_family_key. To use this key, install it on every relay in your family. (Put it in the relay’s KeyDirectory.) Also, store the corresponding family ID in basename.public_family_id. Then enable the corresponding FamilyID option on your relays. This command overwrites these files if they already exist. See https://community.torproject.org/relay/setup/post-install/family-ids/ for more information.

File descriptor to read the passphrase from. Note that unlike with the tor-gencert program, the entire file contents are read and used as the passphrase, including any trailing newlines. If the file descriptor is not specified, the passphrase is read from the terminal by default.

The purpose specifies which type of key certificate to determine the expiration of. The only currently recognised purpose is "sign".

Running tor --key-expiration sign will attempt to find your signing key certificate and will output, both in the logs as well as to stdout. The optional --format argument lets you specify the time format. Currently, iso8601 and timestamp are supported. If --format is not specified, the signing key certificate’s expiration time will be in ISO-8601 format. For example, the output sent to stdout will be of the form: "signing-cert-expiry: 2017-07-25 08:30:15 UTC". If --format timestamp is specified, the signing key certificate’s expiration time will be in Unix timestamp format. For example, the output sent to stdout will be of the form: "signing-cert-expiry: 1500971415".

Tor may support other options beginning with the string "dbg". These are intended for use by developers to debug and test Tor. They are not supported or guaranteed to be stable, and you should probably not use them.

Specify this option if using dynamic hardware acceleration and the engine implementation library resides somewhere other than the OpenSSL default. Can not be changed while tor is running.

When using OpenSSL hardware crypto acceleration attempt to load the dynamic engine of this name. This must be used for any dynamic hardware engine. Names can be verified with the openssl engine command. Can not be changed while tor is running.

If the engine name is prefixed with a "!", then Tor will exit if the engine cannot be loaded.

These options behave as DirAuthority, but they replace fewer of the default directory authorities. Using AlternateDirAuthority replaces the default Tor directory authorities, but leaves the default bridge authorities in place. Similarly, AlternateBridgeAuthority replaces the default bridge authority, but leaves the directory authorities alone.

If non-zero, try to write to disk less frequently than we would otherwise. This is useful when running on flash memory or other media that support only a limited number of writes. (Default: 0)

Limit the maximum token bucket size (also known as the burst) to the given number of bytes in each direction. (Default: 1 GByte)

A token bucket limits the average incoming bandwidth usage on this node to the specified number of bytes per second, and the average outgoing bandwidth usage to that same value. If you want to run a relay in the public network, this needs to be at the very least 75 KBytes for a relay (that is, 600 kbits) or 50 KBytes for a bridge (400 kbits) — but of course, more is better; we recommend at least 250 KBytes (2 mbits) if possible. (Default: 1 GByte)

Note that this option, and other bandwidth-limiting options, apply to TCP data only: They do not count TCP headers or DNS traffic.

Tor uses powers of two, not powers of ten, so 1 GByte is 1024*1024*1024 bytes as opposed to 1 billion bytes.

With this option, and in other options that take arguments in bytes, KBytes, and so on, other formats are also supported. Notably, "KBytes" can also be written as "kilobytes" or "kb"; "MBytes" can be written as "megabytes" or "MB"; "kbits" can be written as "kilobits"; and so forth. Case doesn’t matter. Tor also accepts "byte" and "bit" in the singular. The prefixes "tera" and "T" are also recognized. If no units are given, we default to bytes. To avoid confusion, we recommend writing "bytes" or "bits" explicitly, since it’s easy to forget that "B" means bytes, not bits.

Store cached directory data in DIR. Can not be changed while tor is running. (Default: uses the value of DataDirectory.)

If this option is set to 0, don’t allow the filesystem group to read the CacheDirectory. If the option is set to 1, make the CacheDirectory readable by the default GID. If the option is "auto", then we use the setting for DataDirectoryGroupReadable when the CacheDirectory is the same as the DataDirectory, and 0 otherwise. (Default: auto)

If this value is set, we override the default algorithm for choosing which circuit’s cell to deliver or relay next. It is delivered first to the circuit that has the lowest weighted cell count, where cells are weighted exponentially according to this value (in seconds). If the value is -1, it is taken from the consensus if possible else it will fallback to the default value of 30. Minimum: 1, Maximum: 2147483647. This can be defined as a float value. This is an advanced option; you generally shouldn’t have to mess with it. (Default: -1)

In its first form, when set along with a corresponding Bridge line, the Tor client forwards its traffic to a SOCKS-speaking proxy on "IP:PORT". (IPv4 addresses should written as-is; IPv6 addresses should be wrapped in square brackets.) It’s the duty of that proxy to properly forward the traffic to the bridge.

In its second form, when set along with a corresponding Bridge line, the Tor client launches the pluggable transport proxy executable in path-to-binary using options as its command-line options, and forwards its traffic to it. It’s the duty of that proxy to properly forward the traffic to the bridge. (Default: none)

If this option is set to 1, general purpose traffic will use Conflux which is traffic splitting among multiple legs (circuits). Onion services are not supported at the moment. Default value is set to "auto" meaning the consensus is used to decide unless set. (Default: auto)

This option configures the user experience that the client requests from the exit, for data that the exit sends to the client. The default is "throughput", which maximizes throughput. "Latency" will tell the exit to only use the circuit with lower latency for all data. The lowmem versions minimize queue usage memory at the client. (Default: "throughput")

The minimum number of file descriptors that must be available to the Tor process before it will start. Tor will ask the OS for as many file descriptors as the OS will allow (you can find this by "ulimit -H -n"). If this number is less than ConnLimit, then Tor will refuse to start.

Tor relays need thousands of sockets, to connect to every other relay. If you are running a private bridge, you can reduce the number of sockets that Tor uses. For example, to limit Tor to 500 sockets, run "ulimit -n 500" in a shell. Then start tor in the same shell, with ConnLimit 500. You may also need to set DisableOOSCheck 0.

Unless you have severely limited sockets, you probably don’t need to adjust ConnLimit itself. It has no effect on Windows, since that platform lacks getrlimit(). (Default: 1000)

If set, Tor will tell the kernel to attempt to shrink the buffers for all sockets to the size specified in ConstrainedSockSize. This is useful for virtual servers and other environments where system level TCP buffers may be limited. If you’re on a virtual server, and you encounter the "Error creating network socket: No buffer space available" message, you are likely experiencing this problem.

The preferred solution is to have the admin increase the buffer pool for the host itself via /proc/sys/net/ipv4/tcp_mem or equivalent facility; this configuration option is a second-resort.

The DirPort option should also not be used if TCP buffers are scarce. The cached directory requests consume additional sockets which exacerbates the problem.

You should not enable this feature unless you encounter the "no buffer space available" issue. Reducing the TCP buffers affects window size for the TCP stream and will reduce throughput in proportion to round trip time on long paths. (Default: 0)

When ConstrainedSockets is enabled the receive and transmit buffers for all sockets will be set to this limit. Must be a value between 2048 and 262144, in 1024 byte increments. Default of 8192 is recommended.

If set, Tor will accept connections on this port and allow those connections to control the Tor process using the Tor Control Protocol (described in control-spec.txt in torspec). Note: unless you also specify one or more of HashedControlPassword or CookieAuthentication, setting this option will cause Tor to allow any process on the local host to control it. (Setting both authentication methods means either method is sufficient to authenticate to Tor.) This option is required for many Tor controllers; most use the value of 9051. If a unix domain socket is used, you may quote the path using standard C escape sequences. You can specify this directive multiple times, to bind to multiple address/port pairs. Set it to "auto" to have Tor pick a port for you. (Default: 0)

Recognized flags are:

If this option is set to 0, don’t allow the filesystem group to read the control port file. If the option is set to 1, make the control port file readable by the default GID. (Default: 0)

If set, Tor writes the address and port of any control port it opens to this address. Usable by controllers to learn the actual control port when ControlPort is set to "auto".

Like ControlPort, but listens on a Unix domain socket, rather than a TCP socket. 0 disables ControlSocket. (Unix and Unix-like systems only.) (Default: 0)

If this option is set to 0, don’t allow the filesystem group to read and write unix sockets (e.g. ControlSocket). If the option is set to 1, make the control socket readable and writable by the default GID. (Default: 0)

If this option is set to 1, allow connections on the control port when the connecting process knows the contents of a file named "control_auth_cookie", which Tor will create in its data directory. This authentication method should only be used on systems with good filesystem security. (Default: 0)

If set, this option overrides the default location and file name for Tor’s cookie file. (See CookieAuthentication.)

If this option is set to 0, don’t allow the filesystem group to read the cookie file. If the option is set to 1, make the cookie file readable by the default GID. [Making the file readable by other groups is not yet implemented; let us know if you need this for some reason.] (Default: 0)

If this option is set, then Tor’s rate-limiting applies not only to remote connections, but also to connections to private addresses like 127.0.0.1 or 10.0.0.1. This is mostly useful for debugging rate-limiting. (Default: 0)

Store working data in DIR. Can not be changed while tor is running. (Default: ~/.tor if your home directory is not /; otherwise, /var/lib/tor. On Windows, the default is your ApplicationData folder.)

If this option is set to 0, don’t allow the filesystem group to read the DataDirectory. If the option is set to 1, make the DataDirectory readable by the default GID. (Default: 0)

Use a nonstandard authoritative directory server at the provided address and port, with the specified key fingerprint. This option can be repeated many times, for multiple authoritative directory servers. Flags are separated by spaces, and determine what kind of an authority this directory is. By default, an authority is not authoritative for any directory style or version unless an appropriate flag is given.

Tor will use this authority as a bridge authoritative directory if the "bridge" flag is set. If a flag "orport=orport" is given, Tor will use the given port when opening encrypted tunnels to the dirserver. If a flag "weight=num" is given, then the directory server is chosen randomly with probability proportional to that weight (default 1.0). If a flag "v3ident=fp" is given, the dirserver is a v3 directory authority whose v3 long-term signing key has the fingerprint fp. Lastly, if an "ipv6=[ipv6address]:orport" flag is present, then the directory authority is listening for IPv6 connections on the indicated IPv6 address and OR Port.

Tor will contact the authority at ipv4address to download directory documents. Clients always use the ORPort. Relays usually use the DirPort, but will use the ORPort in some circumstances. If an IPv6 ORPort is supplied, clients will also download directory documents at the IPv6 ORPort, if they are configured to use IPv6.

If no DirAuthority line is given, Tor will use the default directory authorities. NOTE: this option is intended for setting up a private Tor network with its own directory authorities. If you use it, you will be distinguishable from other users, because you won’t believe the same authorities they do.

When configured to use both directory authorities and fallback directories, the directory authorities also work as fallbacks. They are chosen with their regular weights, multiplied by this number, which should be 1.0 or less. The default is less than 1, to reduce load on authorities. (Default: 0.1)

If set to 1, Tor will attempt to lock all current and future memory pages, so that memory cannot be paged out. Windows, OS X and Solaris are currently not supported. We believe that this feature works on modern Gnu/Linux distributions, and that it should work on *BSD systems (untested). This option requires that you start your Tor as root, and you should use the User option to properly reduce Tor’s privileges. Can not be changed while tor is running. (Default: 0)

If set to 1, Tor will attempt to prevent basic debugging attachment attempts by other processes. This may also keep Tor from generating core files if it crashes. It has no impact for users who wish to attach if they have CAP_SYS_PTRACE or if they are root. We believe that this feature works on modern Gnu/Linux distributions, and that it may also work on *BSD systems (untested). Some modern Gnu/Linux systems such as Ubuntu have the kernel.yama.ptrace_scope sysctl and by default enable it as an attempt to limit the PTRACE scope for all user processes by default. This feature will attempt to limit the PTRACE scope for Tor specifically - it will not attempt to alter the system wide ptrace scope as it may not even exist. If you wish to attach to Tor with a debugger such as gdb or strace you will want to set this to 0 for the duration of your debugging. Normal users should leave it on. Disabling this option while Tor is running is prohibited. (Default: 1)

When this option is set, we don’t listen for or accept any connections other than controller connections, and we close (and don’t reattempt) any outbound connections. Controllers sometimes use this option to avoid using the network until Tor is fully configured. Tor will make still certain network-related calls (like DNS lookups) as a part of its configuration process, even if DisableNetwork is set. (Default: 0)

If this option is set to 1, we always try to include a relay’s Ed25519 ID when telling the preceding relay in a circuit to extend to it. If this option is set to 0, we never include Ed25519 IDs when extending circuits. If the option is set to "auto", we obey a parameter in the consensus document. (Default: auto)

Open this port to listen for Extended ORPort connections from your pluggable transports.
(Default: DataDirectory/extended_orport_auth_cookie)

If set, this option overrides the default location and file name for the Extended ORPort’s cookie file — the cookie file is needed for pluggable transports to communicate through the Extended ORPort.

If this option is set to 0, don’t allow the filesystem group to read the Extended OR Port cookie file. If the option is set to 1, make the cookie file readable by the default GID. [Making the file readable by other groups is not yet implemented; let us know if you need this for some reason.] (Default: 0)

When tor is unable to connect to any directory cache for directory info (usually because it doesn’t know about any yet) it tries a hard-coded directory. Relays try one directory authority at a time. Clients try multiple directory authorities and FallbackDirs, to avoid hangs on startup if a hard-coded directory is down. Clients wait for a few seconds between each attempt, and retry FallbackDirs more often than directory authorities, to reduce the load on the directory authorities.

FallbackDirs should be stable relays with stable IP addresses, ports, and identity keys. They must have a DirPort.

By default, the directory authorities are also FallbackDirs. Specifying a FallbackDir replaces Tor’s default hard-coded FallbackDirs (if any). (See DirAuthority for an explanation of each flag.)

If set to 1, Tor will always fetch directory information like other directory caches, even if you don’t meet the normal criteria for fetching early. Normal users should leave it off. (Default: 0)

If set to 1, Tor will fetch directory information before other directory caches. It will attempt to download directory information closer to the start of the consensus period. Normal users should leave it off. (Default: 0)

If set to 0, Tor will never fetch any hidden service descriptors from the rendezvous directories. This option is only useful if you’re using a Tor controller that handles hidden service fetches for you. (Default: 1)

If set to 0, Tor will never fetch any network status summaries or server descriptors from the directory servers. This option is only useful if you’re using a Tor controller that handles directory fetches for you. (Default: 1)

If set to 1, Tor will fetch every consensus flavor, and all server descriptors and authority certificates referenced by those consensuses, except for extra info descriptors. When this option is 1, Tor will also keep fetching descriptors, even when idle. If set to 0, Tor will avoid fetching useless descriptors: flavors that it is not using to build circuits, and authority certificates it does not trust. When Tor hasn’t built any application circuits, it will go idle, and stop fetching descriptors. This option is useful if you’re using a tor client with an external parser that uses a full consensus. This option fetches all documents except extrainfo descriptors, DirCache fetches and serves all documents except extrainfo descriptors, DownloadExtraInfo* fetches extrainfo documents, and serves them if DirCache is on, and UseMicrodescriptors changes the flavor of consensuses and descriptors that is fetched and used for building circuits. (Default: 0)

If non-zero, try to use built-in (static) crypto hardware acceleration when available. Can not be changed while tor is running. (Default: 0)

Allow connections on the control port if they present the password whose one-way hash is hashed_password. You can compute the hash of a password by running "tor --hash-password password". You can provide several acceptable passwords by using more than one HashedControlPassword line.

Tor will make all its directory requests through this host:port (or host:80 if port is not specified), rather than connecting directly to any directory servers. (DEPRECATED: As of 0.3.1.0-alpha you should use HTTPSProxy.)

If defined, Tor will use this username:password for Basic HTTP proxy authentication, as in RFC 2617. This is currently the only form of HTTP proxy authentication that Tor supports; feel free to submit a patch if you want it to support others. (DEPRECATED: As of 0.3.1.0-alpha you should use HTTPSProxyAuthenticator.)

Tor will make all its OR (SSL) connections through this host:port (or host:443 if port is not specified), via HTTP CONNECT rather than connecting directly to servers. You may want to set FascistFirewall to restrict the set of ports you might try to connect to, if your HTTPS proxy only allows connecting to certain ports.

If defined, Tor will use this username:password for Basic HTTPS proxy authentication, as in RFC 2617. This is currently the only form of HTTPS proxy authentication that Tor supports; feel free to submit a patch if you want it to support others.

To keep firewalls from expiring connections, send a padding keepalive cell every NUM seconds on open connections that are in use. (Default: 5 minutes)

On Linux, when we are started as root and we switch our identity using the User option, the KeepBindCapabilities option tells us whether to try to retain our ability to bind to low ports. If this value is 1, we try to keep the capability; if it is 0 we do not; and if it is auto, we keep the capability only if we are configured to listen on a low port. Can not be changed while tor is running. (Default: auto.)

Send all messages between minSeverity and maxSeverity to the standard output stream, the standard error stream, or to the system log. (The "syslog" value is only supported on Unix.) Recognized severity levels are debug, info, notice, warn, and err. We advise using "notice" in most cases, since anything more verbose may provide sensitive information to an attacker who obtains the logs. If only one severity level is given, all messages of that level or higher will be sent to the listed destination.

Some low-level logs may be sent from signal handlers, so their destination logs must be signal-safe. These low-level logs include backtraces, logging function errors, and errors in code called by logging functions. Signal-safe logs are always sent to stderr or stdout. They are also sent to a limited number of log files that are configured to log messages at error severity from the bug or general domains. They are never sent as syslogs, control port log events, or to any API-based log destinations.

As above, but send log messages to the listed filename. The "Log" option may appear more than once in a configuration file. Messages are sent to all the logs that match their severity level.

As above, but select messages by range of log severity and by a set of "logging domains". Each logging domain corresponds to an area of functionality inside Tor. You can specify any number of severity ranges for a single log statement, each of them prefixed by a comma-separated list of logging domains. You can prefix a domain with ~ to indicate negation, and use * to indicate "all domains". If you specify a severity range without a list of domains, it matches all domains.

This is an advanced feature which is most useful for debugging one or two of Tor’s subsystems at a time.

The currently recognized domains are: general, crypto, net, config, fs, protocol, mm, http, app, control, circ, rend, bug, dir, dirserv, or, edge, acct, hist, handshake, heartbeat, channel, sched, guard, consdiff, dos, process, pt, btrack, and mesg. Domain names are case-insensitive.

For example, "Log [handshake]debug [~net,~mm]info notice stdout" sends to stdout: all handshake messages of any severity, all info-and-higher messages from domains other than networking and memory management, and all messages of severity notice or higher.

If 1, Tor includes message domains with each log message. Every log message currently has at least one domain; most currently have exactly one. This doesn’t affect controller log messages. (Default: 0)

Set the resolution of timestamps in Tor’s logs to NUM milliseconds. NUM must be positive and either a divisor or a multiple of 1 second. Note that this option only controls the granularity written by Tor to a file or console log. Tor does not (for example) "batch up" log messages to affect times logged by a controller, times attached to syslog messages, or the mtime fields on log files. (Default: 1 second)

If set, we will not advertise more than this amount of bandwidth for our BandwidthRate. Server operators who want to reduce the number of clients who ask to build circuits through them (since this is proportional to advertised bandwidth rate) can thus reduce the CPU demands on their server without impacting network performance.

Unparseable descriptors (e.g. for votes, consensuses, routers) are logged in separate files by hash, up to the specified size in total. Note that only files logged during the lifetime of this Tor process count toward the total; this is intended to be used to debug problems without opening live servers to resource exhaustion attacks. (Default: 10 MBytes)

WARNING: Before enabling this, it is important to understand that exposing tor metrics publicly is dangerous to the Tor network users. Please take extra precaution and care when opening this port. Set a very strict access policy with MetricsPortPolicy and consider using your operating systems firewall features for defense in depth.
We recommend, for the prometheus format, that the only address that can access this port should be the Prometheus server itself. Remember that the connection is unencrypted (HTTP) hence consider using a tool like stunnel to secure the link from this port to the server.
If set, open this port to listen for an HTTP GET request to "/metrics". Upon a request, the collected metrics in the the tor instance are formatted for the given format and then sent back. If this is set, MetricsPortPolicy must be defined else every request will be rejected.
Supported format is "prometheus" which is also the default if not set. The Prometheus data model can be found here: https://prometheus.io/docs/concepts/data_model/
The tor metrics are constantly collected and they solely consists of counters. Thus, asking for those metrics is very lightweight on the tor process. (Default: None)
As an example, here only 5.6.7.8 will be allowed to connect:

MetricsPort 1.2.3.4:9035
MetricsPortPolicy accept 5.6.7.8

Set an entrance policy for the MetricsPort, to limit who can access it. The policies have the same form as exit policies below, except that port specifiers are ignored. For multiple entries, this line can be used multiple times. It is a reject all by default policy. (Default: None)
Please, keep in mind here that if the server collecting metrics on the MetricsPort is behind a NAT, then everything behind it can access it. This is similar for the case of allowing localhost, every users on the server will be able to access it. Again, strongly consider using a tool like stunnel to secure the link or to strengthen access control.

If this option is set to 1, then Tor will never launch another executable, regardless of the settings of ClientTransportPlugin or ServerTransportPlugin. Once this option has been set to 1, it cannot be set back to 0 without restarting Tor. (Default: 0)

Make all outbound connections originate from the IP address specified. This is only useful when you have multiple network interfaces, and you want all of Tor’s outgoing connections to use a single one. This option may be used twice, once with an IPv4 address and once with an IPv6 address. IPv6 addresses should be wrapped in square brackets. This setting will be ignored for connections to the loopback addresses (127.0.0.0/8 and ::1), and is not used for DNS requests as well.

Make all outbound exit connections originate from the IP address specified. This option overrides OutboundBindAddress for the same IP version. This option may be used twice, once with an IPv4 address and once with an IPv6 address. IPv6 addresses should be wrapped in square brackets. This setting will be ignored for connections to the loopback addresses (127.0.0.0/8 and ::1).

Make all outbound non-exit (relay and other) connections originate from the IP address specified. This option overrides OutboundBindAddress for the same IP version. This option may be used twice, once with an IPv4 address and once with an IPv6 address. IPv6 addresses should be wrapped in square brackets. This setting will be ignored for connections to the loopback addresses (127.0.0.0/8 and ::1).

Make Tor instance periodically check for presence of a controller process with given PID and terminate itself if this process is no longer alive. Polling interval is 15 seconds.

If this option is set manually, or via the "perconnbwburst" consensus field, Tor will use it for separate rate limiting for each connection from a non-relay. (Default: 0)

If this option is set manually, or via the "perconnbwrate" consensus field, Tor will use it for separate rate limiting for each connection from a non-relay. (Default: 0)

Request that pluggable transports makes all outbound connections originate from the IP address specified. Because outgoing connections are handled by the pluggable transport itself, it is not possible for Tor to enforce whether the pluggable transport honors this option. This option overrides OutboundBindAddress for the same IP version. This option may be used twice, once with an IPv4 address and once with an IPv6 address. IPv6 addresses should be wrapped in square brackets. This setting will be ignored for connections to the loopback addresses (127.0.0.0/8 and ::1).

On startup, write our PID to FILE. On clean shutdown, remove FILE. Can not be changed while tor is running.

If 1, Tor will log with severity 'warn' various cases of other parties not following the Tor specification. Otherwise, they are logged with severity 'info'. (Default: 0)

If not 0, limit the maximum token bucket size (also known as the burst) for _relayed traffic_ to the given number of bytes in each direction. They do not include directory fetches by the relay (from authority or other relays), because that is considered "client" activity. (Default: 0) RelayBandwidthBurst defaults to the value of RelayBandwidthRate if unset.

If not 0, a separate token bucket limits the average incoming bandwidth usage for _relayed traffic_ on this node to the specified number of bytes per second, and the average outgoing bandwidth usage to that same value. Relayed traffic currently is calculated to include answers to directory requests, but that may change in future versions. They do not include directory fetches by the relay (from authority or other relays), because that is considered "client" activity. (Default: 0) RelayBandwidthRate defaults to the value of RelayBandwidthBurst if unset.

Tells an authority, or other node tracking node reliability and history, that fine-grained information about nodes can be discarded when it hasn’t changed for a given amount of time. (Default: 24 hours)

If 1, Tor forks and daemonizes to the background. This option has no effect on Windows; instead you should use the --service command-line option. Can not be changed while tor is running. (Default: 0)

Tor can scrub potentially sensitive strings from log messages (e.g. addresses) by replacing them with the string [scrubbed]. This way logs can still be useful, but they don’t leave behind personally identifying information about what sites a user might have visited.

If this option is set to 0, Tor will not perform any scrubbing, if it is set to 1, all potentially sensitive strings are replaced. If it is set to relay, all log messages generated when acting as a relay are sanitized, but all messages generated when acting as a client are not. Note: Tor may not heed this option when logging at log levels more verbose than Notice. (Default: 1)

If set to 1, Tor will run securely through the use of a syscall sandbox. Otherwise the sandbox will be disabled. The option only works on Linux-based operating systems, and only when Tor has been built with the libseccomp library. Note that this option may be incompatible with some versions of libc, and some kernel versions. This option can not be changed while tor is running.

When the Sandbox is 1, the following options can not be changed when tor is running: Address, ConnLimit, CookieAuthFile, DirPortFrontPage, ExtORPortCookieAuthFile, Logs, ServerDNSResolvConfFile, ClientOnionAuthDir (and any files in it won’t reload on HUP signal).

Launching new Onion Services through the control port is not supported with current syscall sandboxing implementation.

Tor must remain in client or server mode (some changes to ClientOnly and ORPort are not allowed). Currently, if Sandbox is 1, ControlPort command "GETINFO address" will not work.

When using %include in the tor configuration files, reloading the tor configuration is not supported after adding new configuration files or directories.

(Default: 0)

Specify the scheduler type that tor should use. The scheduler is responsible for moving data around within a Tor process. This is an ordered list by priority which means that the first value will be tried first and if unavailable, the second one is tried and so on. It is possible to change these values at runtime. This option mostly effects relays, and most operators should leave it set to its default value. (Default: KIST,KISTLite,Vanilla)

The possible scheduler types are:
KIST: Kernel-Informed Socket Transport. Tor will use TCP information from the kernel to make informed decisions regarding how much data to send and when to send it. KIST also handles traffic in batches (see KISTSchedRunInterval) in order to improve traffic prioritization decisions. As implemented, KIST will only work on Linux kernel version 2.6.39 or higher.

KISTLite: Same as KIST but without kernel support. Tor will use all the same mechanics as with KIST, including the batching, but its decisions regarding how much data to send will not be as good. KISTLite will work on all kernels and operating systems, and the majority of the benefits of KIST are still realized with KISTLite.

Vanilla: The scheduler that Tor used before KIST was implemented. It sends as much data as possible, as soon as possible. Vanilla will work on all kernels and operating systems.

If KIST or KISTLite is used in the Schedulers option, this controls at which interval the scheduler tick is. If the value is 0 msec, the value is taken from the consensus if possible else it will fallback to the default 10 msec. Maximum possible value is 100 msec. (Default: 0 msec)

If KIST is used in Schedulers, this is a multiplier of the per-socket limit calculation of the KIST algorithm. (Default: 1.0)

Tor will make all OR connections through the SOCKS 4 proxy at host:port (or host:1080 if port is not specified).

Tor will make all OR connections through the SOCKS 5 proxy at host:port (or host:1080 if port is not specified).

If defined, authenticate to the SOCKS 5 server using username and password in accordance to RFC 1929. Both username and password must be between 1 and 255 characters.

When logging to syslog, adds a tag to the syslog identity such that log entries are marked with "Tor-tag". Can not be changed while tor is running. (Default: none)

Tor will use the given protocol to make all its OR (SSL) connections through a TCP proxy on host:port, rather than connecting directly to servers. You may want to set FascistFirewall to restrict the set of ports you might try to connect to, if your proxy only allows connecting to certain ports. There is no equivalent option for directory connections, because all Tor client versions that support this option download directory documents via OR connections.

The only protocol supported right now is 'haproxy'. This option is only for
clients. (Default: none) +

The HAProxy version 1 proxy protocol is described in detail at
https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt +

Both source IP address and source port will be set to zero.

If 1, Tor will overwrite logs at startup and in response to a HUP signal, instead of appending to them. (Default: 0)

If this option is set to 0, don’t allow the filesystem group to read and write unix sockets (e.g. SocksPort unix:). If the option is set to 1, make the Unix socket readable and writable by the default GID. (Default: 0)

Use Tor’s default hard-coded FallbackDirs (if any). (When a FallbackDir line is present, it replaces the hard-coded FallbackDirs, regardless of the value of UseDefaultFallbackDirs.) (Default: 1)

On startup, setuid to this user and setgid to their primary group. Can not be changed while tor is running.

When this option is disabled, Tor blocks hostnames containing illegal characters (like @ and :) rather than sending them to an exit node to be resolved. This helps trap accidental attempts to resolve URLs and so on. (Default: 0)

When this option is enabled, and we get a request to resolve an address that ends with one of the suffixes in AutomapHostsSuffixes, we map an unused virtual address to that address, and return the new virtual address. This is handy for making ".onion" addresses work with applications that resolve an address and then connect to it. (Default: 0)

A comma-separated list of suffixes to use with AutomapHostsOnResolve. The "." suffix is equivalent to "all addresses." (Default: .exit,.onion).

When set along with UseBridges, instructs Tor to use the relay at "IP:ORPort" as a "bridge" relaying into the Tor network. If "fingerprint" is provided (using the same format as for DirAuthority), we will verify that the relay running at that location has the right fingerprint. We also use fingerprint to look up the bridge descriptor at the bridge authority, if it’s provided and if UpdateBridgesFromAuthority is set too.

If "transport" is provided, it must match a ClientTransportPlugin line. We then use that pluggable transport’s proxy to transfer data to the bridge, rather than connecting to the bridge directly. Some transports use a transport-specific method to work out the remote address to connect to. These transports typically ignore the "IP:ORPort" specified in the bridge line.

Tor passes any "key=val" settings to the pluggable transport proxy as per-connection arguments when connecting to the bridge. Consult the documentation of the pluggable transport for details of what arguments it supports.

If set to 0, Tor will not pad client circuits with additional cover traffic. Only clients may set this option. This option should be offered via the UI to mobile users for use where bandwidth may be expensive. If set to 1, padding will be negotiated as per the consensus and relay support (unlike ConnectionPadding, CircuitPadding cannot be force-enabled). (Default: 1)

If set to 1, Tor will only use circuit padding algorithms that have low overhead. Only clients may set this option. This option should be offered via the UI to mobile users for use where bandwidth may be expensive. (Default: 0)

Initial delay in seconds for when clients should download consensuses from authorities if they are bootstrapping (that is, they don’t have a usable, reasonably live consensus). Only used by clients fetching from a list of fallback directory mirrors. This schedule is advanced by (potentially concurrent) connection attempts, unlike other schedules, which are advanced by connection failures. (Default: 6)

Initial delay in seconds for when clients should download consensuses from authorities if they are bootstrapping (that is, they don’t have a usable, reasonably live consensus). Only used by clients which don’t have or won’t fetch from a list of fallback directory mirrors. This schedule is advanced by (potentially concurrent) connection attempts, unlike other schedules, which are advanced by connection failures. (Default: 0)

Initial delay in seconds for when clients should download consensuses from fallback directory mirrors if they are bootstrapping (that is, they don’t have a usable, reasonably live consensus). Only used by clients fetching from a list of fallback directory mirrors. This schedule is advanced by (potentially concurrent) connection attempts, unlike other schedules, which are advanced by connection failures. (Default: 0)

Try this many simultaneous connections to download a consensus before waiting for one to complete, timeout, or error out. (Default: 3)

If true, Tor does not believe any anonymously retrieved DNS answer that tells it that an address resolves to an internal address (like 127.0.0.1 or 192.168.0.1). This option prevents certain browser-based attacks; it is not allowed to be set on the default network. (Default: 1)

Path to the directory containing v3 hidden service authorization files. Each file is for a single onion address, and the files MUST have the suffix ".auth_private" (i.e. "bob_onion.auth_private"). The content format MUST be:
<onion-address>:descriptor:x25519:<base32-encoded-privkey>
The <onion-address> MUST NOT have the ".onion" suffix. The <base32-encoded-privkey> is the base32 representation of the raw key bytes only (32 bytes for x25519). See Appendix G in the rend-spec-v3.txt file of torspec for more information.

If set to 1, Tor will not run as a relay or serve directory requests, even if the ORPort, ExtORPort, or DirPort options are set. (This config option is mostly unnecessary: we added it back when we were considering having Tor clients auto-promote themselves to being relays if they were stable and fast enough. The current behavior is simply that Tor is a client unless ORPort, ExtORPort, or DirPort are configured.) (Default: 0)

If this option is set to 1, Tor prefers a directory port with an IPv6 address over one with IPv4, for direct connections, if a given directory server has both. (Tor also prefers an IPv6 DirPort if IPv4Client is set to 0.) If this option is set to auto, clients prefer IPv4. Other things may influence the choice. This option breaks a tie to the favor of IPv6. (Default: auto) (DEPRECATED: This option has had no effect for some time.)

If this option is set to 1, Tor prefers an OR port with an IPv6 address over one with IPv4 if a given entry node has both. (Tor also prefers an IPv6 ORPort if IPv4Client is set to 0.) If this option is set to auto, Tor bridge clients prefer the configured bridge address, and other clients prefer IPv4. Other things may influence the choice. This option breaks a tie to the favor of IPv6. (Default: auto)

If true, Tor does not try to fulfill requests to connect to an internal address (like 127.0.0.1 or 192.168.0.1) unless an exit node is specifically requested (for example, via a .exit hostname, or a controller request). If true, multicast DNS hostnames for machines on the local network (of the form *.local) are also rejected. (Default: 1)

If this option is set to 0, Tor will avoid connecting to directory servers and entry nodes over IPv4. Note that clients with an IPv4 address in a Bridge, proxy, or pluggable transport line will try connecting over IPv4 even if ClientUseIPv4 is set to 0. (Default: 1)

If this option is set to 1, Tor might connect to directory servers or entry nodes over IPv6. For IPv6 only hosts, you need to also set ClientUseIPv4 to 0 to disable IPv4. Note that clients configured with an IPv6 address in a Bridge, proxy, or pluggable transportline will try connecting over IPv6 even if ClientUseIPv6 is set to 0. (Default: 1)

This option governs Tor’s use of padding to defend against some forms of traffic analysis. If it is set to auto, Tor will send padding only if both the client and the relay support it. If it is set to 0, Tor will not send any padding cells. If it is set to 1, Tor will still send padding for client connections regardless of relay support. Only clients may set this option. This option should be offered via the UI to mobile users for use where bandwidth may be expensive. (Default: auto)

If set to 1, Tor will not not hold OR connections open for very long, and will send less padding on these connections. Only clients may set this option. This option should be offered via the UI to mobile users for use where bandwidth may be expensive. (Default: 0)

If non-zero, open this port to listen for UDP DNS requests, and resolve them anonymously. This port only handles A, AAAA, and PTR requests---it doesn’t handle arbitrary DNS request types. Set the port to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to multiple addresses/ports. See SocksPort for an explanation of isolation flags. (Default: 0)

If true, Tor downloads and caches "extra-info" documents. These documents contain information about servers other than the information in their regular server descriptors. Tor does not use this information for anything itself; to save bandwidth, leave this option turned off. (Default: 0)

If 1, Tor will not put two servers whose IP addresses are "too close" on the same circuit. Currently, two addresses are "too close" if they lie in the same /16 range. (Default: 1)

If 1, Tor will only create outgoing connections to ORs running on ports that your firewall allows (defaults to 80 and 443; see FirewallPorts). This will allow you to run Tor as a client behind a firewall with restrictive policies, but will not allow you to run as a server behind such a firewall. If you prefer more fine-grained control, use ReachableAddresses instead.

A list of ports that your firewall allows you to connect to. Only used when FascistFirewall is set. This option is deprecated; use ReachableAddresses instead. (Default: 80, 443)

Open this port to listen for proxy connections using the "HTTP CONNECT" protocol instead of SOCKS. Set this to 0 if you don’t want to allow "HTTP CONNECT" connections. Set the port to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to multiple addresses/ports. If multiple entries of this option are present in your configuration file, Tor will perform stream isolation between listeners by default. See SocksPort for an explanation of isolation flags. (Default: 0)

A list of ports for services that tend to have long-running connections (e.g. chat and interactive shells). Circuits for streams that use these ports will contain only high-uptime nodes, to reduce the chance that a node will go down before the stream is finished. Note that the list is also honored for circuits (both client and service side) involving hidden services whose virtual port is in this list. (Default: 21, 22, 706, 1863, 5050, 5190, 5222, 5223, 6523, 6667, 6697, 8300)

When a request for address arrives to Tor, it will transform to newaddress before processing it. For example, if you always want connections to www.example.com to exit via torserver (where torserver is the fingerprint of the server), use "MapAddress www.example.com www.example.com.torserver.exit". If the value is prefixed with a "*.", matches an entire domain. For example, if you always want connections to example.com and any if its subdomains to exit via torserver (where torserver is the fingerprint of the server), use "MapAddress *.example.com *.example.com.torserver.exit". (Note the leading "*." in each part of the directive.) You can also redirect all subdomains of a domain to a single address. For example, "MapAddress *.example.com www.example.com". If the specified exit is not available, or the exit can not connect to the site, Tor will fail any connections to the mapped address.+
NOTES:

Feel free to reuse a circuit that was first used at most NUM seconds ago, but never attach a new stream to a circuit that is too old. For hidden services, this applies to the last time a circuit was used, not the first. Circuits with streams constructed with SOCKS authentication via SocksPorts that have KeepAliveIsolateSOCKSAuth also remain alive for MaxCircuitDirtiness seconds after carrying the last such stream. (Default: 10 minutes)

Do not allow more than NUM circuits to be pending at a time for handling client streams. A circuit is pending if we have begun constructing it, but it has not yet been completely constructed. (Default: 32)

Open this port to listen for connections from old versions of ipfw (as included in old versions of FreeBSD, etc) using the NATD protocol. Use 0 if you don’t want to allow NATD connections. Set the port to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to multiple addresses/ports. If multiple entries of this option are present in your configuration file, Tor will perform stream isolation between listeners by default. See SocksPort for an explanation of isolation flags.

This option is only for people who cannot use TransPort. (Default: 0)

Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds)

These options override the default behavior of Tor’s (currently experimental) path bias detection algorithm. To try to find broken or misbehaving guard nodes, Tor looks for nodes where more than a certain fraction of circuits through that guard fail to get built.

The PathBiasCircThreshold option controls how many circuits we need to build through a guard before we make these checks. The PathBiasNoticeRate, PathBiasWarnRate and PathBiasExtremeRate options control what fraction of circuits must succeed through a guard so we won’t write log messages. If less than PathBiasExtremeRate circuits succeed and PathBiasDropGuards is set to 1, we disable use of that guard.

When we have seen more than PathBiasScaleThreshold circuits through a guard, we scale our observations by 0.5 (governed by the consensus) so that new observations don’t get swamped by old ones.

By default, or if a negative value is provided for one of these options, Tor uses reasonable defaults from the networkstatus consensus document. If no defaults are available there, these options default to 150, .70, .50, .30, 0, and 300 respectively.

Similar to the above options, these options override the default behavior of Tor’s (currently experimental) path use bias detection algorithm.

Where as the path bias parameters govern thresholds for successfully building circuits, these four path use bias parameters govern thresholds only for circuit usage. Circuits which receive no stream usage are not counted by this detection algorithm. A used circuit is considered successful if it is capable of carrying streams or otherwise receiving well-formed responses to RELAY cells.

By default, or if a negative value is provided for one of these options, Tor uses reasonable defaults from the networkstatus consensus document. If no defaults are available there, these options default to 20, .80, .60, and 100, respectively.

Tor clients don’t build circuits for user traffic until they know about enough of the network so that they could potentially construct enough of the possible paths through the network. If this option is set to a fraction between 0.25 and 0.95, Tor won’t build circuits until it has enough descriptors or microdescriptors to construct that fraction of possible paths. Note that setting this option too low can make your Tor client less anonymous, and setting it too high can prevent your Tor client from bootstrapping. If this option is negative, Tor will use a default value chosen by the directory authorities. If the directory authorities do not choose a value, Tor will default to 0.6. (Default: -1)

A comma-separated list of IP addresses and ports that your firewall allows you to connect to. The format is as for the addresses in ExitPolicy, except that "accept" is understood unless "reject" is explicitly provided. For example, 'ReachableAddresses 99.0.0.0/8, reject 18.0.0.0/8:80, accept *:80' means that your firewall allows connections to everything inside net 99, rejects port 80 connections to net 18, and accepts connections to port 80 otherwise. (Default: 'accept *:*'.)

Like ReachableAddresses, a list of addresses and ports. Tor will obey these restrictions when fetching directory information, using standard HTTP GET requests. If not set explicitly then the value of ReachableAddresses is used. If HTTPProxy is set then these connections will go through that proxy. (DEPRECATED: This option has had no effect for some time.)

Like ReachableAddresses, a list of addresses and ports. Tor will obey these restrictions when connecting to Onion Routers, using TLS/SSL. If not set explicitly then the value of ReachableAddresses is used. If HTTPSProxy is set then these connections will go through that proxy.

The separation between ReachableORAddresses and ReachableDirAddresses is only interesting when you are connecting through proxies (see HTTPProxy and HTTPSProxy). Most proxies limit TLS connections (which Tor uses to connect to Onion Routers) to port 443, and some limit HTTP GET requests (which Tor uses for fetching directory information) to port 80.

When this option is enabled, Tor will reject application connections that use unsafe variants of the socks protocol — ones that only provide an IP address, meaning the application is doing a DNS resolve first. Specifically, these are socks4 and socks5 when not doing remote DNS. (Default: 0)

When this option is enabled, Tor will make a notice-level log entry for each connection to the Socks port indicating whether the request used a safe socks protocol or an unsafe one (see SafeSocks). This helps to determine whether an application using Tor is possibly leaking DNS requests. (Default: 0)

Tells Tor to issue a warnings whenever the user tries to make an anonymous connection to one of these ports. This option is designed to alert users to services that risk sending passwords in the clear. (Default: 23,109,110,143)

Like WarnPlaintextPorts, but instead of warning about risky port uses, Tor will instead refuse to make the connection. (Default: None)

Set an entrance policy for this server, to limit who can connect to the SocksPort and DNSPort ports. The policies have the same form as exit policies below, except that port specifiers are ignored. Any address not matched by some entry in the policy is accepted.

Open this port to listen for connections from SOCKS-speaking applications. Set this to 0 if you don’t want to allow application connections via SOCKS. Set it to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to multiple addresses/ports. If a unix domain socket is used, you may quote the path using standard C escape sequences. Most flags are off by default, except where specified. Flags that are on by default can be disabled by putting "No" before the flag name. (Default: 9050)

NOTE: Although this option allows you to specify an IP address other than localhost, you should do so only with extreme caution. The SOCKS protocol is unencrypted and (as we use it) unauthenticated, so exposing it in this way could leak your information to anybody watching your network, and allow anybody to use your computer as an open proxy.

If multiple entries of this option are present in your configuration file, Tor will perform stream isolation between listeners by default. The isolation flags arguments give Tor rules for which streams received on this SocksPort are allowed to share circuits with one another. Recognized isolation flags are:

Other recognized flags for a SocksPort are: