> ## 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.

# bluesky.media.mime_allowed

> Bluesky accepts jpeg/png/webp/gif images and mp4 video. Other formats are rejected.

## What it checks

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

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

## Why

The PDS (Personal Data Server) blob endpoint enforces the same allowlist. Sending HEIC, BMP, MOV, etc. produces a `BlobUnsupportedMimeType` error from Bluesky — opaque, async, hard to debug. We catch it locally.

## Failure response

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

## Remediation

Re-encode the asset. ImageMagick, sharp, ffmpeg — any of them. For video, `ffmpeg -i input.mov -c:v libx264 -c:a aac output.mp4` produces a Bluesky-compatible mp4.

## Related

* [`bluesky.media.image_size_max`](/preflight/bluesky-media-image_size_max)
* [`bluesky.media.video_size_max`](/preflight/bluesky-media-video_size_max)