When you post publicly on Threads with Fediverse sharing enabled, users on Mastodon and other ActivityPub servers can reply to your posts. If a particular Mastodon server hosts spam, harassment, or content you do not want associated with your Threads account, you can block the entire server from replying to you. This article explains how to find the server name and block it using the Threads settings. You will learn the exact steps to stop replies from a specific Mastodon instance without leaving Threads.
Key Takeaways: Blocking a Mastodon Server in Threads
- Settings > Privacy > Fediverse sharing: Turn on Fediverse sharing to allow replies from Mastodon and other servers.
- Blocked servers list: Add the full domain name of the Mastodon server (for example, mastodon.social) to prevent any user on that server from replying to your Threads posts.
- Reply preview: Check the reply preview in the Threads compose window to see which server a reply came from before you block it.
What Happens When You Block a Mastodon Server in Threads
Threads uses the ActivityPub protocol to connect with Mastodon and other Fediverse servers. When you enable Fediverse sharing in your Threads settings, your public posts are visible to users on those servers. Those users can reply to your posts, and their replies appear in your Threads notifications and conversation threads. Blocking a whole Mastodon server means you stop all replies from every account that is hosted on that specific server. The server itself is not notified, and your Threads profile remains visible to users on other servers. This feature is useful if a server is known for spam, hate speech, or coordinated harassment. You can block as many servers as you need.
Prerequisites for Blocking a Mastodon Server
Before you can block a Mastodon server, you must have Fediverse sharing enabled on your Threads account. If Fediverse sharing is off, no Mastodon users can reply to you, but you also cannot see any replies from the Fediverse. To enable it, go to your Threads profile, tap the menu icon in the top-right corner, select Settings, then Privacy, and turn on Fediverse sharing. You also need to know the exact domain name of the Mastodon server you want to block. Domain names look like mastodon.social, fosstodon.org, or hachyderm.io. If you see a reply from a Mastodon user, you can find the server name by looking at the reply details in Threads.
Steps to Block a Mastodon Server From Replying to Your Threads
- Open the Threads app or website
Launch Threads on your mobile device or go to threads.net in your browser. Sign in to the Instagram account linked to your Threads profile. - Go to your profile
Tap your profile picture in the bottom-right corner of the mobile app, or click your profile picture in the top-right of the web interface. - Open Settings
Tap the menu icon (two horizontal lines) in the top-right corner, then select Settings from the menu. - Navigate to Privacy
In the Settings menu, tap Privacy. This opens the privacy controls for your Threads account. - Find Blocked servers
Scroll down to the Fediverse section. Tap Blocked servers. This shows a list of Mastodon servers you have already blocked. If you have not blocked any, the list is empty. - Add the server domain name
Tap Add server or the plus icon. Enter the full domain name of the Mastodon server you want to block. For example, type mastodon.social. Do not include https:// or www. Tap Save or the check mark to confirm. - Confirm the block
Threads shows a confirmation message. The server is now added to your blocked list. Any future replies from accounts on that server will not appear in your Threads posts or notifications.
After you block a server, existing replies from that server remain visible unless you delete them manually. To remove a server from the blocked list later, go back to Settings > Privacy > Blocked servers, tap the server name, and select Unblock.
How to Find the Mastodon Server Name From a Reply
If you receive a reply from a Mastodon user and want to block their entire server, you need to identify the server domain name. In the Threads mobile app, tap the reply to open the conversation. Look for the user’s handle below their name. A Mastodon handle looks like @username@server.domain. The part after the @ sign is the server domain name. For example, in @johndoe@mastodon.social, the server is mastodon.social. On the web version, hover over the user’s name to see their full handle in a tooltip. Copy the server domain name exactly as it appears.
What Happens After You Block a Server
Blocking a Mastodon server stops all replies from users on that server. Those users cannot reply to your Threads posts, and their replies do not appear in your notifications. However, they can still see your public posts if they view your profile on their server. The block only affects replies, not visibility. If you want to prevent a specific user from seeing your posts, block that individual user instead of the whole server. To block an individual user, go to their profile and tap the menu icon, then select Block.
Common Issues When Blocking a Mastodon Server
I entered the server domain name but it says invalid
Make sure you typed the domain name correctly. Common mistakes include adding https://, www., or a trailing slash. The correct format is server.domain only. For example, use fosstodon.org, not https://fosstodon.org. If the server is not reachable or does not federate with Threads, the block may not apply. Try blocking a different server to test the feature.
Replies from a blocked server still appear
Replies that were posted before you blocked the server remain visible. You must delete them manually. To delete a reply, long-press the reply and select Delete. After that, no new replies from that server will appear.
I cannot find the Blocked servers option in Settings
This option appears only if Fediverse sharing is enabled. Go to Settings > Privacy > Fediverse sharing and turn it on. If the option is still missing, your Threads account may be in a region where Fediverse sharing is not yet available. Check the Threads help center for supported countries.
I blocked a server by mistake
Go to Settings > Privacy > Blocked servers, tap the server name, and select Unblock. Replies from that server will start appearing again after the next time a user on that server replies to your post.
Blocking a Server vs Blocking an Individual User
| Item | Block a Server | Block an Individual User |
|---|---|---|
| Scope | All accounts on that Mastodon server | One specific account only |
| Where to block | Settings > Privacy > Blocked servers | User profile > menu > Block |
| Effect on replies | Stops all replies from that server | Stops replies from that one user only |
| Effect on visibility | Users on blocked server can still see your posts | Blocked user cannot see your posts |
| Reversal | Unblock server in settings | Unblock user from profile |
You can use both methods together. For example, block a server that hosts spam accounts, and also block individual users who continue to harass you from other servers.
Blocking a whole Mastodon server gives you control over who can engage with your Threads posts. Use the Blocked servers list in Settings to add or remove servers as needed. Check the replies on your public posts regularly to see if any new servers need to be blocked. For persistent issues, consider turning off Fediverse sharing temporarily until you identify the source of unwanted replies.