Threads opened its API in 2024 and it is one of the cleaner ones: a post is created, then published, and that is the whole protocol. The traps are in the counting. Preflight publishes text, pictures, carousels, video, polls and reply chains to a Threads account and checks each against the rules the Threads API applies, including the one about bytes.
| Threads through Preflight | What the API allows |
|---|---|
| Text limit | 500 characters |
| Media | Pictures and video, up to 20 files |
| Pictures | Up to 8 MB each |
| Video | 1 GB, up to 5 min, 23 to 60 fps |
| Thread in one go | Yes |
| First comment | No |
| Alt text | Yes |
| Edit after publishing | No, the API has no edit |
| Delete from Preflight | Yes |
| Comments | Read and reply |
| Figures reported | views, likes, comments, shares |
| Retention and traffic sources | No |
What goes out
A text post, up to 20 pictures or one video, a poll with two to four answers, and a chain of replies posted under the first post in one go, which is what Threads calls a thread. Each post can carry a topic tag and a reply control that decides who may answer: everyone, people you follow, or people you mention. Pictures take alt text. How to schedule Threads posts walks through the composer; this page is about the connection and the rules.
Connecting an account
Connect with Threads. Preflight asks for the basic profile, publishing, insights, delete, and two separate reply permissions, because Meta reviews reading replies and answering them separately and both are needed for the comments screen to show a reply and let you answer it. Any Threads account works; there is no business-account requirement as on Instagram.
What is checked before publishing
The rules on /limits/threads. The 500-character limit is counted in UTF-8 bytes, so an emoji costs up to four and an accented letter two; Preflight counts the same way and shows the figure. More than five links in a post is refused. Pictures must be JPEG or PNG up to 8 MB, no wider than 10:1, and are warned when outside 320 to 1,440 pixels wide, where Threads resizes them. Video is MP4 or MOV up to 1 GB and five minutes at 23 to 60 frames per second. A poll must have two to four answers of up to 25 characters and goes only on a text post; on a post with pictures it is left off and you are told. Every part of a reply chain is measured against the same 500 bytes.
What the API will not do
A published Threads post cannot be edited; it can be deleted from Preflight. Replies are read, answered and hidden; only the author can delete a reply, so other people's cannot be, and there is no endpoint for liking a reply. There is no first comment separate from the chain, but the second part of a chain does the same job. Figures come back for views, likes, replies and reposts.
In the API
Chains, polls, topic tags and reply control are fields in the public API and parameters in the MCP server, with the byte count applied on both. Threads is on every plan at pricing.
Questions people ask
- Why does Threads refuse a post that is under 500 characters?
- Threads counts bytes, not characters. Emoji take up to four bytes and accented letters two, so a 420-character post with emoji can be over the limit. Preflight counts in bytes too and shows the figure before you schedule.
- Can Preflight post a Threads poll?
- Yes, on a text post: two to four answers of up to 25 characters each. Threads attaches polls to text posts only, so on a post with pictures the poll is left off and the composer says so.
- Can I edit a Threads post after publishing?
- No. The Threads API has no edit endpoint for anyone. A published post can be deleted from Preflight and posted again.