You want your Threads posts to appear on Mastodon and also allow replies from Mastodon users to flow back into Threads. This two-way connection is called round-trip posting. It relies on the ActivityPub protocol, which Threads supports in a limited way. This walkthrough explains how to set up that connection and what you can realistically expect from it.
Key Takeaways: Threads to Mastodon Round-Trip Posting
- Profile > Privacy > Fediverse sharing: Enables your public Threads posts to be shared on Mastodon and other ActivityPub servers.
- Public profile requirement: Only public Threads profiles can use Fediverse sharing; private profiles cannot.
- Mastodon replies appear in Threads: Replies from Mastodon users show up under your Threads post, but you cannot reply to them from Threads.
What Round-Trip Posting Means for Threads and Mastodon
Threads uses the ActivityPub protocol to share public posts with Mastodon and other Fediverse services. When you enable Fediverse sharing, each public Threads post gets copied to a Mastodon server that Threads operates. Mastodon users can see, boost, and reply to that post. Those replies then appear in the Threads app under the original post.
The connection is not a full two-way sync. You can see Mastodon replies in Threads, but you cannot reply to them from Threads. To respond, you must open your Mastodon account or use a separate Fediverse client. Also, Direct Messages and private posts never leave Threads.
Before you start, ensure your Threads profile is set to public. A private profile cannot use Fediverse sharing. You also need a Mastodon account on any server. You do not need to follow your Threads account from Mastodon to see its posts, but following it makes replies easier to track.
What Gets Shared
Only text and images from public Threads posts are shared. Videos and links are not included in the Fediverse copy. The post appears on Mastodon as a regular post from the Threads server. The display name and profile picture from your Threads profile are used.
What Does Not Get Shared
Reactions such as likes on Threads do not appear on Mastodon. Quote posts from Threads are not shared. Threads replies from other Threads users do not appear on Mastodon. Only the original public post and its Mastodon replies travel between the two platforms.
Steps to Enable Round-Trip Posting Between Threads and Mastodon
- Set your Threads profile to public
Open the Threads app. Tap your profile icon in the bottom right. Tap the Edit profile button. Under Profile visibility, select Public. If your profile is private, the Fediverse sharing option is hidden. - Enable Fediverse sharing
Tap the two-line menu icon in the top right corner. Tap Privacy. Tap Fediverse sharing. Toggle the switch to On. A confirmation dialog appears. Tap Turn on to confirm. - Post a public message on Threads
Tap the compose icon. Write a short message with an optional image. Tap Post. The post appears on Threads immediately. The Fediverse copy is sent within a few minutes. - Find your post on Mastodon
Log in to your Mastodon account. Search for the Threads server handle. The handle is usually @yourusername@threads.net. For example, if your Threads username is johndoe, search for @johndoe@threads.net. Your post appears as a new post from that handle. - Reply to the post from Mastodon
On Mastodon, click the reply icon under your Threads post. Type a reply and post it. The reply appears in the Threads app under the original post after a short delay, usually under 5 minutes. - Check the reply in Threads
Open the Threads app. Go to your profile and tap the original post. Scroll down. The Mastodon reply appears with the Mastodon user’s display name and avatar. You cannot reply to it from Threads.
Common Issues and Limitations With Round-Trip Posting
Mastodon replies do not appear in Threads
This usually happens because the Threads server has not processed the reply yet. Wait 5 to 10 minutes. If the reply still does not appear, check that the Mastodon account you used is not blocked by your Threads profile. Also confirm that the original Threads post is still public.
Threads posts do not appear on Mastodon
Verify that Fediverse sharing is turned on in Privacy settings. If the toggle is off, turn it on and repost the message. Posts created before enabling Fediverse sharing are not shared retroactively. Only new public posts are sent to the Fediverse.
Cannot reply to Mastodon replies from Threads
This is by design. Threads does not support sending replies back to Mastodon. To respond, open your Mastodon account or use a Fediverse client like Mastodon’s web interface. You can also mention the Mastodon user in a new Threads post, but that creates a separate conversation thread.
Images from Threads do not appear on Mastodon
Images are shared, but the Mastodon server may resize or strip metadata. If the image is too large, Mastodon may reject it. Keep images under 8 MB and use common formats like JPEG or PNG. Videos are never shared to Mastodon.
Threads vs Mastodon Native Federation: Round-Trip Capabilities Compared
| Item | Threads to Mastodon | Mastodon to Mastodon |
|---|---|---|
| Post visibility | Only public posts | Public and unlisted posts |
| Reply direction | Mastodon to Threads only | Both directions fully |
| Media support | Images only | Images, videos, and audio |
| Reactions | Not shared | Favorites and boosts shared |
| Direct Messages | Not supported | Supported between servers |
Round-trip posting between Threads and Mastodon is a one-way conversation with replies coming back. For full two-way interaction, use Mastodon directly. The Threads integration is best for broadcasting public content to a wider Fediverse audience.