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

# Mastodon media guidelines

> See how OpenPMM applies the media limits reported by each Mastodon instance.

A Mastodon instance owns its media limits. Two instances can have different limits. OpenPMM reads the limits from your connected instance. Read [Media guidelines](/docs/media/overview) for the general rules.

## Self-reply chains

Repeat the Post `body` value to publish a Mastodon thread. OpenPMM publishes
the first status, then replies to the previous status for every later body
item. Media can attach to each body item, and any body item can contain media
without text. If publication stops part-way, a retry resumes at the first
missing reply.

## Limits from your instance

OpenPMM applies these values from the instance:

| Property                  | Applies to                                      |
| ------------------------- | ----------------------------------------------- |
| Maximum media attachments | The number of assets in one post                |
| Accepted file types       | Video and image assets                          |
| Maximum video size        | Video assets                                    |
| Maximum video frame rate  | Video assets                                    |
| Maximum video pixels      | Video assets. Multiply the width by the height. |
| Maximum image size        | Image assets                                    |

Mastodon documents no fixed video contract, so OpenPMM has no static video limit for this channel. The OpenPMM 500 MiB upload limit still applies.

## Image limits

A Mastodon server reports its own image limits. OpenPMM reads these values from
the destination:

| Property  | Source                 |
| --------- | ---------------------- |
| Format    | `supported_mime_types` |
| File size | `image_size_limit`     |
| Pixels    | `image_matrix_limit`   |

OpenPMM converts an image and makes the file smaller to obey the values that the
server reports. See [Media compatibility](/docs/guides/media-compatibility).

## Missing values

## Provider documentation

[Mastodon instance configuration](https://docs.joinmastodon.org/entities/Instance/#configuration)