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Configuring your environment

Setting environment variables for your Mastodon installation.

Last modified Sun Dec 18, 2022
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Mastodon uses environment variables as its configuration.

For convenience, it can read them from a flat file called .env.production in the Mastodon directory (called a “dotenv” file), but they can always be overridden by a specific process. For example, systemd service files can read environment variables from an EnvironmentFile or from inline definitions with Environment, so you can have different configuration parameters for specific services. They can also be specified when calling Mastodon from the command line.

Basic

Federation and display

LOCAL_DOMAIN

This is the unique identifier of your server in the network. It cannot be safely changed later, as changing it will cause remote servers to confuse your existing accounts with entirely new ones. It has to be the domain name you are running the server under (without the protocol part, e.g. just example.com).

WEB_DOMAIN

WEB_DOMAIN is an optional environment variable allowing to install Mastodon on one domain, while having the users’ handles on a different domain, e.g. addressing users as @alice@example.com but accessing Mastodon on mastodon.example.com. This may be useful if your domain name is already used for a different website but you still want to use it as a Mastodon identifier because it looks better or shorter.

As with LOCAL_DOMAIN, WEB_DOMAIN cannot be safely changed once set, as this will confuse remote servers that knew of your previous settings and may break communication with them or make it unreliable. As the issues lie with remote servers’ understanding of your accounts, re-installing Mastodon from scratch will not fix the issue. Therefore, please be extremely cautious when setting up LOCAL_DOMAIN and WEB_DOMAIN.

To install Mastodon on mastodon.example.com in such a way it can serve @alice@example.com, set LOCAL_DOMAIN to example.com and WEB_DOMAIN to mastodon.example.com. This also requires additional configuration on the server hosting example.com to redirect or proxy requests to https://example.com/.well-known/webfinger to https://mastodon.example.com/.well-known/webfinger. For instance, with nginx, the configuration could look like the following:

location /.well-known/webfinger {
  add_header Access-Control-Allow-Origin '*';
  return 301 https://mastodon.example.com$request_uri;
}

ALTERNATE_DOMAINS

If you have multiple domains pointed at your Mastodon server, this setting will allow Mastodon to recognize itself when users are addressed using those other domains. Separate the domains by commas, e.g. foo.com,bar.com

ALLOWED_PRIVATE_ADDRESSES

Comma-separated specific addresses/subnets allowed in outgoing HTTP queries.

AUTHORIZED_FETCH

Also called “secure mode”. When set to true, the following changes occur:

  • Mastodon will stop generating linked-data signatures for public posts, which prevents them from being re-distributed efficiently but without precise control. Since a linked-data object with a signature is entirely self-contained, it can be passed around without making extra requests to the server where it originates.
  • Mastodon will require HTTP signature authentication on ActivityPub representations of public posts and profiles, which are normally available without any authentication. Profiles will only return barebones technical information when no authentication is supplied.
  • Prior to v4.0.0: Mastodon will require any REST/streaming API access to have a user context (i.e. having gone through an OAuth authorization screen with an active user), when normally some API endpoints are available without any authentication.

As a result, through the authentication mechanism and avoiding re-distribution mechanisms that do not have your server in the loop, it becomes possible to enforce who can and cannot retrieve even public content from your server, e.g. servers whose domains you have blocked.

Unfortunately, secure mode is not without its drawbacks, which is why it is not enabled by default. Not all software in the fediverse can support it fully, in particular some functionality will be broken with Mastodon servers older than 3.0; you lose some useful functionality even with up-to-date servers since linked-data signatures are used to make public conversation threads more complete; and because an authentication mechanism on public content means no caching is possible, it comes with an increased computational cost.
Secure mode does not hide HTML representations of public posts and profiles. HTML is a more lossy format compared to first-class ActivityPub representations or the REST API but it is still a potential vector for scraping content.

LIMITED_FEDERATION_MODE

When set to true, Mastodon will restrict federation to servers you have manually approved only, as well as disable all public pages and some REST APIs. Limited federation mode is based on secure mode (AUTHORIZED_FETCH).

When switching an existing instance to limited federation mode, the following command should be used to remove any already existent data on non-allowed domains:

tootctl domain purge --limited-federation-mode
This mode is intended for private use only, such as in academic institutions or internal company networks, as it effectively creates a data silo, which is contrary to Mastodon’s mission of decentralization.
This setting was known as WHITELIST_MODE prior to 3.1.5.

DISALLOW_UNAUTHENTICATED_API_ACCESS

As of Mastodon v4.0.0, the web app is now used to render all requests, even for logged-out viewers. In order to make these views work, the web app makes public API requests in order to fetch accounts and statuses. If you would like to disallow this, then set this variable to true. Note that disallowing unauthenticated API access will cause profile and post permalinks to return an error to logged-out users, essentially making it so that the only ways to view content is to either log in locally or fetch it via ActivityPub.

SINGLE_USER_MODE

If set to true, the frontpage of your Mastodon server will always redirect to the first profile in the database and registrations will be disabled.

DEFAULT_LOCALE

By default, Mastodon will automatically detect the visitor’s language from browser headers and display the Mastodon interface in that language (if it’s supported). If you are running a language-specific or regional server, that behaviour may mislead visitors who do not speak your language into signing up on your server. For this reason, you may want to set this variable to a specific language.

Example value: de

Supported languages:

  • ar
  • ast
  • bg
  • bn
  • br
  • ca
  • co
  • cs
  • cy
  • da
  • de
  • el
  • en
  • eo
  • es
  • es-AR
  • et
  • eu
  • fa
  • fi
  • fr
  • ga
  • gl
  • he
  • hi
  • hr
  • hu
  • hy
  • id
  • io
  • is
  • it
  • ja
  • ka
  • kab
  • kk
  • kn
  • ko
  • lt
  • lv
  • mk
  • ml
  • mr
  • ms
  • nl
  • nn
  • no
  • oc
  • pl
  • pt-BR
  • pt-PT
  • ro
  • ru
  • sk
  • sl
  • sq
  • sr
  • sr-Latn
  • sv
  • ta
  • te
  • th
  • tr
  • uk
  • ur
  • vi
  • zh-CN
  • zh-HK
  • zh-TW

Secrets

SECRET_KEY_BASE

Generate with rake secret. Changing it will break all active browser sessions.

OTP_SECRET

Generate with rake secret. Changing it will break two-factor authentication.

VAPID_PRIVATE_KEY

Generate with rake mastodon:webpush:generate_vapid_key. Changing it will break push notifications.

VAPID_PUBLIC_KEY

Generate with rake mastodon:webpush:generate_vapid_key. Changing it will break push notifications.

Deployment

RAILS_ENV

Environment. Can be production, development, or test. If you are running Mastodon on your personal computer for development purposes, use development. That is also the default. If you are running Mastodon online, use production. Mastodon will load different configuration defaults based on the environment.

This variable cannot be defined in dotenv (.env) files as it’s used before they are loaded.

RAILS_SERVE_STATIC_FILES

If set to true, Mastodon will answer requests for files in its public directory. This may be necessary if the reverse proxy (e.g. nginx) has no file system access to the public directory itself, such as in a containerized environment. It is a suboptimal setting because serving static files directly from the file system will always be much faster than serving them through the Ruby on Rails process.

RAILS_LOG_LEVEL

Determines the amount of logs generated by Mastodon. Defaults to info, which generates a log entry about every request served by Mastodon and every background job processed by Mastodon. This can be useful but can get quite noisy and strain the I/O of your machine if there is a lot of traffic/activity. In that case, warn is recommended, which will only output information about things that are going wrong, and otherwise stay quiet. Possible values are debug, info, warn, error, fatal and unknown.

TRUSTED_PROXY_IP

Tells the Mastodon web and streaming processes which IPs act as your trusted reverse proxy (e.g. nginx, Cloudflare). It affects how Mastodon determines the source IP of each request, which is used for important rate limits and security functions. If the value is set incorrectly then Mastodon could use the IP of the reverse proxy instead of the actual source.

By default the loopback and private network address ranges are trusted. Specifically:

  • 127.0.0.1/8
  • ::1/128
  • 10.0.0.0/8
  • 172.16.0.0/12
  • 192.168.0.0/16
  • fc00::/7

If you’re using a single reverse proxy and it runs on the same machine or is in the same private network as your Mastodon web and streaming processes then you most likely don’t need to modify this setting and can use the default. Or if you’re using multiple reverse proxy servers and they’re all in the same private network as your Mastodon web and streaming processes then, again, the default should be fine. However, if you’re using a reverse proxy server that reaches your Mastodon web and streaming servers via a public IP address (for example if you’re using Cloudflare or a similar proxy) then you’ll need to set this variable. It should be the IPs of all reverse proxies in use, as a comma-separated list of IPs or IP ranges using CIDR notation. Note that when this variable is set the default ranges (mentioned above) will no longer be trusted, so if you have both an external reverse proxy and a proxy on localhost then you must include the IPs (or IP ranges) of both.

SOCKET

Instead of binding to an IP address like 127.0.0.1, you may bind to a Unix socket. This variable is process-specific, e.g. you need different values for every process, and it works for both web (Puma) processes and streaming API (Node.js) processes.

This variable cannot be defined in dotenv (.env) files as it’s used before they are loaded.

PORT

If you are not using Unix sockets, this defines which port the process will listen on. This variable is process-specific, e.g. you need different values for every process, and it works for both web (Puma) processes and streaming API (Node.js) processes. By default, web listens on 3000 and streaming API on 4000.

This variable cannot be defined in dotenv (.env) files as it’s used before they are loaded.

NODE_ENV

Equivalent to RAILS_ENV, but for the streaming API (Node.js).

This variable cannot be defined in dotenv (.env) files as it’s used before they are loaded.

BIND

If you are not using Unix sockets, this defines the IP to which the process will bind. Multiple processes can bind to the same IP as long as they listen on different ports. Defaults to 127.0.0.1.

This variable cannot be defined in dotenv (.env) files as it’s used before they are loaded.

Scaling options

What is Mastodon?

SIDEKIQ_CONCURRENCY

Added in 4.1. Specific to Sidekiq, this variable determines how many different processes Sidekiq forks into. Defaults to 5.

WEB_CONCURRENCY

Specific to Puma, this variable determines how many different processes Puma forks into. Defaults to 2.

MAX_THREADS

Specific to Puma, this variable determines how many threads each Puma process maintains. Defaults to 5.

PERSISTENT_TIMEOUT

Specific to Puma, this variable determines how long Puma should wait before closing a connection. Defaults to 20.

PREPARED_STATEMENTS

By default, Mastodon uses the prepared statements feature of PostgreSQL, which offers some performance advantages. This feature is not available if you are using a connection pool where connections are shared between transactions and must thus be set to false. When you are scaling up, the advantages of having a transaction-based connection pool outweigh those provided by prepared statements.

STREAMING_API_BASE_URL

The streaming API can be deployed to a different domain/subdomain. This may improve the performance of the streaming API as in the default configuration long-lived streaming API requests are proxied through nginx, while serving the streaming API from a different domain/subdomain would allow one to skip nginx entirely.

Example value: wss://streaming.example.com

STREAMING_CLUSTER_NUM

Specific to the streaming API, this variable determines how many different processes the streaming API forks into. Defaults to the number of CPU cores minus one.

Backend

PostgreSQL

DB_HOST

Defaults to localhost.

DB_USER

Defaults to mastodon.

DB_NAME

Defaults to mastodon_production.

DB_PASS

No default.

DB_PORT

Defaults to 5432.

DB_POOL

How many database connections to pool in the process. This value should cover every thread in the process, for this reason, it defaults to the value of MAX_THREADS.

DB_SSLMODE

Postgres’s SSL mode. Defaults to prefer.

DATABASE_URL

If provided, takes precedence over DB_HOST, DB_USER, DB_NAME, DB_PASS and DB_PORT.

Example value: postgresql://user:password@localhost:5432

Redis

It is possible to use a separate Redis server for volatile cache. You may wish to do so if your Redis server starts getting overwhelmed.

REDIS_HOST

Defaults to localhost.

REDIS_PORT

Defaults to 6379.

REDIS_URL

If provided, takes precedence over REDIS_HOST and REDIS_PORT.

Example value: redis://user:password@localhost:6379

REDIS_NAMESPACE

If provided, namespaces all Redis keys. This allows sharing the same Redis database between different projects or Mastodon servers.

CACHE_REDIS_HOST

Defaults to value of REDIS_HOST.

CACHE_REDIS_PORT

Defaults to value of REDIS_PORT.

CACHE_REDIS_URL

If provided, takes precedence over CACHE_REDIS_HOST and CACHE_REDIS_PORT. Defaults to value of REDIS_URL.

CACHE_REDIS_NAMESPACE

Defaults to value of REDIS_NAMESPACE.

SIDEKIQ_REDIS_URL

Elasticsearch

What is Mastodon?

ES_ENABLED

If set to true, Mastodon will use Elasticsearch for its search functions.

ES_HOST

Host of the Elasticsearch server. Defaults to localhost

ES_PORT

Port of the Elasticsearch server. Defaults to 9200

ES_USER

Used for optionally authenticating with ElasticSearch

ES_PASS

Used for optionally authenticating with ElasticSearch

ES_PREFIX

Useful if the Elasticsearch server is shared between multiple projects or different Mastodon servers. Defaults to value of REDIS_NAMESPACE.

StatsD

STATSD_ADDR

If set, Mastodon will log some events and metrics into a StatsD instance identified by its hostname and port.

Example value: localhost:8125

STATSD_NAMESPACE

If set, all StatsD keys will be prefixed with this. Defaults to Mastodon.production when RAILS_ENV is production, Mastodon.development when it’s development, etc.

SMTP email delivery

SMTP_SERVER

SMTP_PORT

SMTP_LOGIN

SMTP_PASSWORD

SMTP_FROM_ADDRESS

SMTP_DOMAIN

SMTP_DELIVERY_METHOD

SMTP_AUTH_METHOD

SMTP_CA_FILE

SMTP_OPENSSL_VERIFY_MODE

SMTP_ENABLE_STARTTLS_AUTO

SMTP_ENABLE_STARTTLS

Set to auto (default), always, or never.

Version history:
4.0.0 - added

SMTP_TLS

SMTP_SSL

File storage

CDN {cdn}

CDN_HOST

You can serve static assets (logos, emojis, CSS, JS, etc) from a separate host, like a CDN (Content Delivery Network) as it can decrease loading times for your users.

Example value: https://assets.example.com

You must serve the files with CORS headers, otherwise some functions of Mastodon’s web UI will not work. For example, Access-Control-Allow-Origin: *

S3_ALIAS_HOST

Similar to CDN_HOST, you may serve user-uploaded files from a separate host. In fact, if you are using external storage like Amazon S3, Minio or Google Cloud, you will by default be serving files from those services’ URLs.

It is extremely recommended to use your own host instead, for a few reasons:

  1. Bandwidth on external storage providers is metered and expensive
  2. You may want to switch to a different provider later without breaking old links

Example value: files.example.com

What is Mastodon?
You must serve the files with CORS headers, otherwise some functions of Mastodon’s web UI will not work. For example, Access-Control-Allow-Origin: *

Local file storage

PAPERCLIP_ROOT_PATH

PAPERCLIP_ROOT_URL

Amazon S3 and compatible

S3_ENABLED

S3_BUCKET

AWS_ACCESS_KEY_ID

AWS_SECRET_ACCESS_KEY

S3_REGION

S3_PROTOCOL

S3_HOSTNAME

S3_ENDPOINT

S3_SIGNATURE_VERSION

S3_OVERRIDE_PATH_STYLE

S3_OPEN_TIMEOUT

S3_READ_TIMEOUT

S3_FORCE_SINGLE_REQUEST

Swift

SWIFT_ENABLED

SWIFT_USERNAME

SWIFT_TENANT

SWIFT_PASSWORD

SWIFT_PROJECT_ID

SWIFT_AUTH_URL

SWIFT_CONTAINER

SWIFT_OBJECT_URL

SWIFT_REGION

SWIFT_DOMAIN_NAME

SWIFT_CACHE_TTL

External authentication

OmniAuth

OMNIAUTH_ONLY

LDAP

LDAP_ENABLED

LDAP_HOST

LDAP_PORT

LDAP_METHOD

LDAP_BASE

LDAP_BIND_DN

LDAP_PASSWORD

LDAP_UID

LDAP_SEARCH_FILTER

LDAP_MAIL

LDAP_UID_CONVERSION_ENABLED

PAM

PAM_ENABLED

PAM_EMAIL_DOMAIN

PAM_DEFAULT_SERVICE

PAM_CONTROLLED_SERVICE

CAS

CAS_ENABLED

CAS_DISPLAY_NAME

CAS_URL

CAS_HOST

CAS_PORT

CAS_SSL

CAS_VALIDATE_URL

CAS_CALLBACK_URL

CAS_LOGOUT_URL

CAS_LOGIN_URL

CAS_UID_FIELD

CAS_CA_PATH

CAS_DISABLE_SSL_VERIFICATION

CAS_UID_KEY

CAS_NAME_KEY

CAS_EMAIL_KEY

CAS_NICKNAME_KEY

CAS_FIRST_NAME_KEY

CAS_LAST_NAME_KEY

CAS_LOCATION_KEY

CAS_IMAGE_KEY

CAS_PHONE_KEY

CAS_SECURITY_ASSUME_EMAIL_IS_VERIFIED

SAML

SAML_ENABLED

SAML_ACS_URL

SAML_ISSUER

SAML_IDP_SSO_TARGET_URL

SAML_IDP_CERT

SAML_IDP_CERT_FINGERPRINT

SAML_NAME_IDENTIFIER_FORMAT

SAML_CERT

SAML_PRIVATE_KEY

SAML_SECURITY_WANT_ASSERTION_SIGNED

SAML_SECURITY_WANT_ASSERTION_ENCRYPTED

SAML_SECURITY_ASSUME_EMAIL_IS_VERIFIED

SAML_ATTRIBUTES_STATEMENTS_UID

SAML_ATTRIBUTES_STATEMENTS_EMAIL

SAML_ATTRIBUTES_STATEMENTS_FULL_NAME

SAML_ATTRIBUTES_STATEMENTS_FIRST_NAME

SAML_ATTRIBUTES_STATEMENTS_LAST_NAME

SAML_UID_ATTRIBUTE

SAML_ATTRIBUTES_STATEMENTS_VERIFIED

SAML_ATTRIBUTES_STATEMENTS_VERIFIED_EMAIL

Hidden services

TOR

What is Mastodon?

http_proxy

http_hidden_proxy

ALLOW_ACCESS_TO_HIDDEN_SERVICE

Limits

Email domains

EMAIL_DOMAIN_ALLOWLIST

If set, registrations will not be possible with any e-mails except those from the specified domains. Pipe-separated values, e.g.: foo.com|bar.com

EMAIL_DOMAIN_DENYLIST

If set, registrations will not be possible with any e-mails from the specified domains. Pipe-separated values, e.g.: foo.com|bar.com

This option is deprecated. You can dynamically block e-mail domains from the admin interface or from the tootctl command-line interface.

Sessions

MAX_SESSION_ACTIVATIONS

How many browser sessions are allowed per-user. Defaults to 10. If a new browser session is created, then the oldest session is deleted, e.g. user in that browser is logged out.

Home feeds

USER_ACTIVE_DAYS

Mastodon stores home feeds in RAM (specifically, in the Redis database). This makes them very fast to access and update, but it also means that you don’t want to keep them there if they’re not used, and you don’t want to spend resources on inserting new items into home feeds that will not be accessed. For this reason, Mastodon periodically clears out home feeds of users who haven’t been online in a while, and if they re-appear, it regenerates those home feeds from database data. By default, users are considered active if they have been online in the past 7 days.

Regeneration of home feeds is computationally expensive, if your Sidekiq is constantly doing it because your users come online every 3 days but your USER_ACTIVE_DAYS is set to 2, then consider adjusting it up.

This setting has no relation to which users are considered active for the purposes of statistics, such as the Monthly Active Users number.

Other

DB migrations

SKIP_POST_DEPLOYMENT_MIGRATIONS

This variable only has any effect when running rake db:migrate and it is extremely specific to the Mastodon upgrade process. There are two types of database migrations, those that run before new code is deployed and running, and those that run after. By default, both types of migrations are executed. If you shut down all Mastodon processes before running migrations, then there is no difference. The variable makes sense for zero-downtime upgrades. You will see in the upgrade instructions of a specific Mastodon version if you need to use it or not.

Uncategorized or unsorted

BUNDLE_GEMFILE

DEEPL_API_KEY

DEEPL_PLAN

LIBRE_TRANSLATE_ENDPOINT

LIBRE_TRANSLATE_API_KEY

CACHE_BUSTER_ENABLED

CACHE_BUSTER_SECRET_HEADER

CACHE_BUSTER_SECRET

GITHUB_REPOSITORY

Defaults to mastodon/mastodon

SOURCE_BASE_URL

Defaults to https://github.com/$GITHUB_REPOSITORY

FFMPEG_BINARY

LOCAL_HTTPS

PATH

MAX_FOLLOWS_THRESHOLD

Defaults to 7500

MAX_FOLLOWS_RATIO

Defaults to 1.1

IP_RETENTION_PERIOD

Defaults to 31536000 (1 year)

SESSION_RETENTION_PERIOD

Defaults to 31536000 (1 year)

BACKTRACE

Set to 1 to allow backtracing to Rails framework code.

DISABLE_SIMPLECOV

EMAIL_DOMAIN_LISTS_APPLY_AFTER_CONFIRMATION

DISABLE_FOLLOWERS_SYNCHRONIZATION

MAX_REQUEST_POOL_SIZE

Defaults to 512.

GITHUB_API_TOKEN

Used in a rake task for generating AUTHORS.md from Github commit history.