You may want to stop federating with a specific Mastodon instance because it hosts content that violates your server’s rules, such as spam, harassment, or illegal material. Federation is the core feature that allows Mastodon instances to exchange posts and profiles across the fediverse. When you block a remote instance at the server level, your instance will no longer fetch or deliver content from that instance. This article explains how to use the admin moderation interface to block a domain, what happens to existing content, and what side effects you should expect.
Key Takeaways: Blocking a Remote Instance in Mastodon
- Administration > Server Rules > Domain Blocks: The exact path to block an entire remote instance from federating with yours.
- Silence vs Suspend: Silence hides content from local timelines; Suspend removes all content and stops all federation.
- Existing content deletion: Suspending a domain deletes all cached media and removes all posts from local timelines and search.
Why You Must Block at the Server Level to Stop Federation
Mastodon instances exchange data using the ActivityPub protocol. When your instance follows a user on a remote instance, or when a remote user follows someone on your instance, both servers begin sending each other new posts, boosts, and notifications. This automatic exchange is called federation.
Individual users cannot stop federation with a specific instance. Blocking a remote user on your instance only prevents that one user from interacting with you. Their instance continues to send data to yours. To stop all data exchange with a remote instance, a server administrator must apply a domain block.
How Domain Blocks Work
A domain block tells your Mastodon server to reject all incoming and outgoing ActivityPub messages from the blocked domain. Your server will stop fetching posts from that domain. It will also stop delivering posts from your users to that domain. The remote instance will no longer appear in the federated timeline. Local users will not be able to follow accounts on the blocked domain, and accounts on the blocked domain will not appear in search results.
Difference Between Silence and Suspend
Mastodon provides two levels of domain blocking: silence and suspend. A silence hides all content from the blocked instance from local timelines and search. Posts from silenced instances still appear in the Home timeline of users who follow accounts on that instance. A suspend removes all content from the blocked instance entirely. No data is displayed anywhere. Suspended instances cannot follow any user on your server. Suspension is the only way to completely stop federation.
Steps to Block a Remote Instance Using the Admin Interface
Only server administrators with the Manage Federation permission can perform these steps. You must be logged in as an admin on your own instance. The web interface is the same on Mastodon 4.x and later versions.
- Open the Administration menu
Click the hamburger icon (three horizontal lines) in the upper left corner of the Mastodon web interface. From the menu that appears, click Preferences at the bottom. In the left sidebar, click Administration. If you do not see Administration, you do not have admin rights on this instance. - Navigate to Server Rules > Domain Blocks
Under the Administration heading in the left sidebar, click Server Rules. Then click Domain Blocks. This page lists all currently blocked domains and allows you to add new ones. - Click the Add New Domain Block button
At the top of the Domain Blocks page, click the Add new domain block button. A form opens with fields for the domain name, severity, and an optional reason. - Enter the domain name
In the Domain field, type the full domain name of the instance you want to block. For example, example.social. Do not include the protocol (https://) or a trailing slash. - Choose the severity level
In the Severity dropdown, select one of two options:
– Silence: Hides content from local timelines and search. Users who already follow accounts on this instance can still see new posts in their Home timeline.
– Suspend: Removes all content from this instance. Stops all federation. Prevents any future interactions. This is the only option to completely stop federation. - Optionally add a reason
In the Reason text box, type a short explanation for the block. This reason is stored in the moderation log and visible to other admins on your instance. It is not shared with the blocked instance. - Block all subdomains if needed
Check the box labeled Block all subdomains if you want to block the entered domain and all subdomains. For example, if you enter bad.example.com and check this box, your server will also block sub.bad.example.com and any other subdomain. - Click the Add Domain Block button
At the bottom of the form, click the Add domain block button. Mastodon will process the block immediately. If you chose Suspend, the server begins deleting cached media and removing posts from the blocked domain from local timelines and search.
If the Block Does Not Take Effect Immediately
Federated Timeline Still Shows Posts From the Blocked Instance
If you silenced the domain, posts from the blocked instance will no longer appear in the federated timeline. If they still appear, your browser may be showing a cached version of the page. Hard refresh the page by pressing Ctrl+F5 on Windows or Cmd+Shift+R on Mac. If posts still appear, verify that the domain block was saved correctly by returning to the Domain Blocks page and confirming the domain is listed.
Local Users Can Still Follow Accounts on the Blocked Instance
If you used the Silence severity, users who already follow accounts on the blocked instance can continue to see new posts from those accounts in their Home timeline. They cannot discover new accounts on that instance through search or the federated timeline. To prevent all following, you must use Suspend instead of Silence.
Blocked Instance Continues to Send Direct Messages
If you used Silence, direct messages from the blocked instance to your users may still be delivered. Direct messages bypass timeline visibility rules. To block all direct message delivery, apply a Suspend. After suspension, no messages of any type will be accepted from the blocked domain.
Domain Block Comparison: Silence vs Suspend
| Item | Silence | Suspend |
|---|---|---|
| Effect on federation | Stops new follows from your instance to the blocked domain | Stops all data exchange completely |
| Existing posts visibility | Hidden from local timelines and search | Deleted from local timelines, search, and media storage |
| Existing followers retained | Yes, users can still see posts from accounts they already follow | No, all follows are removed |
| Direct messages delivered | Yes, direct messages from blocked domain still arrive | No, all messages are rejected |
You now know how to stop federating with a specific instance using the Mastodon admin interface. Apply a Suspend block to completely sever all data exchange with a remote server. For a less aggressive approach, use Silence to hide content while preserving existing follows. After blocking a domain, monitor the Domain Blocks page periodically to ensure the block remains active and that no new federation attempts occur from the blocked domain.