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Integrate with Mastodon

Support level: Community

What is Mastodon?​

Mastodon is free and open-source software for running self-hosted social networking services. It has microblogging features similar to Twitter.

-- https://joinmastodon.org/

Preparation​

The following placeholders are used in this guide:

  • mastodon.company is the FQDN of the Mastodon installation.
  • authentik.company is the FQDN of the authentik installation.
info

This documentation lists only the settings that you need to change from their default values. Be aware that any changes other than those explicitly mentioned in this guide could cause issues accessing your application.

authentik configuration​

Redirect URI changes in authentik 2026.5

In authentik versions earlier than 2026.5, all Redirect URIs are automatically treated as Authorization type. If you are using one of these older authentik versions, add only the Authorization URL to your Redirect URIs and do not configure a Post Logout URI.

To support the integration of Mastodon with authentik, you need to create an application/provider pair in authentik.

Create an application and provider​

  1. Log in to authentik as an administrator and open the authentik Admin interface.

  2. Navigate to Applications > Applications and click New Application to open the application wizard.

    • Application: provide a descriptive name, an optional group for the type of application, the policy engine mode, and optional UI settings. Note the application Slug because you will use it later as <application_slug>.
    • Choose a Provider type: select OAuth2/OpenID Connect as the provider type.
    • Configure the Provider: provide a name (or accept the auto-provided name), the authorization flow to use for this provider, and the following required configurations.
      • Note the Client ID and Client Secret values because they will be required later.
      • Add a Redirect URI of type Strict Authorization as https://mastodon.company/auth/auth/openid_connect/callback.
      • Select any available signing key.
    • Configure Bindings (optional): you can create a binding (policy, group, or user) to manage the listing and access to applications on a user's Application Dashboard page.

  3. Click Submit to save the new application and provider.

Mastodon configuration​

Configure Mastodon's OIDC_ settings by editing .env.production and adding the following values:

.env.production
OIDC_ENABLED=true
OIDC_DISPLAY_NAME=authentik
OIDC_DISCOVERY=true
OIDC_ISSUER=https://authentik.company/application/o/<application_slug>/
OIDC_SCOPE=openid,profile,email
OIDC_UID_FIELD=preferred_username
OIDC_CLIENT_ID=<Client ID from authentik>
OIDC_CLIENT_SECRET=<Client Secret from authentik>
OIDC_REDIRECT_URI=https://mastodon.company/auth/auth/openid_connect/callback
OIDC_SECURITY_ASSUME_EMAIL_IS_VERIFIED=true
Stable Mastodon usernames

This configuration uses the authentik preferred_username claim as the Mastodon user identifier so that new Mastodon usernames match authentik usernames. Disable the Allow users to change username setting in authentik to prevent authentication issues after username changes.

Alternatively, you can set OIDC_UID_FIELD=sub to use authentik's stable subject identifier instead of the username.

Restart the Mastodon web service for the changes to take effect.

Configuration verification​

To confirm that authentik is properly configured with Mastodon, open Mastodon and log in using the authentik login option.

Resources​