> ## Documentation Index
> Fetch the complete documentation index at: https://docs.letmepost.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# threads.media.mime_allowed

> Threads accepts jpeg/png/webp images and mp4/mov video.

## What it checks

For images: `mimeType ∈ { image/jpeg, image/png, image/webp }`.
For videos: `mimeType ∈ { video/mp4, video/quicktime }`.

The mime is sniffed from the resolved bytes, not trusted from the file extension.

## Why

Meta's Threads create-container endpoint rejects HEIC, BMP, AVI, etc. with opaque `code 100` errors. Catching the mime mismatch locally surfaces a useful rule + remediation.

## Failure response

```json theme={"system"}
{
  "error": {
    "code": "preflight_failed",
    "rule": "threads.media.mime_allowed",
    "platform": "threads",
    "message": "Image mime type 'image/heic' is not allowed on Threads.",
    "remediation": "Use one of: image/jpeg, image/png, image/webp."
  }
}
```

## Remediation

Re-encode the asset:

```sh theme={"system"}
# HEIC → JPEG
magick input.heic output.jpg

# AVI → MP4
ffmpeg -i input.avi -c:v libx264 -c:a aac output.mp4
```

## Related

* [`threads.media.image_size_max`](/preflight/threads-media-image_size_max)
* [`threads.media.video_size_max`](/preflight/threads-media-video_size_max)
* [`instagram.media.mime_allowed`](/preflight/instagram-media-mime_allowed) — IG is stricter (JPEG-only).