You can attach audio, video or photos to Mastodon posts. To do this click on the attachment logo (which is a paperclip 📎 on the web, apps will usually have a photo icon).

Attachments can be:

-Up to four PNG, JPG or GIF images of 8 megabytes

OR

-One MP4, M4V, MOV or WebM video of 40 megabytes

OR

-One MP3, OGG, WAV, FLAC, OPUS, AAC, M4A or 3GP audio file of 40 megabytes

There is no length limit on audio or video, only a file size limit. Remember to add text descriptions for attachments! 👍