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Mastodon specifications

Find current Mastodon specifications for profiles, posts and shared media. Compare dimensions, aspect ratios, file formats and source guidance.

6 specifications 6 official

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Showing 6 specifications

Profile Avatar

Official
Dimensions400×400
Aspect ratio1:1
FormatImage
File typeWEBP, PNG, GIF, JPG
File sizeUp to 2MB
Status Official specification
Reviewed
Source Official guide
NotesMastodon downsizes profile avatars to 400×400px. Instance administrators can customize some server limits.

Header (Profile Banner)

Official
Dimensions1500×500
Aspect ratio3:1
FormatImage
File typeWEBP, PNG, GIF, JPG
File sizeUp to 2MB
Status Official specification
Reviewed
Source Official guide
NotesMastodon downsizes profile headers to 1500×500px. Instance administrators can customize some server limits.

Post Image

Official
PlacementStatus Attachment
Dimensions3840×2160
Aspect ratio16:9
Supported ratios16:9 – 1:1 – 4:5
FormatImage
File typePNG, JPG, HEIF, WEBP, AVIF
File sizeUp to 16MB
Text Primary: Default post limit: 500 characters
Requirements
  • Images are downscaled to 8.3 megapixels
  • Up to 4 images per post
  • Add alt text and set a focal point when useful
Status Official specification
Reviewed
Source Mastodon Documentation
NotesInstance administrators can configure different limits; these are the defaults documented by Mastodon.

Animated GIF Attachment

Official
PlacementStatus Attachment
Dimensions1280×720
Aspect ratio16:9
FormatVideo
File typeGIF, soundless MP4 or WebM
File sizeUp to 16MB
MinimumGIF must remain below 1 megapixel
Requirements
  • One animated GIF per post
  • Converted to a soundless looping MP4
Status Official specification
Reviewed
Source Mastodon Documentation
NotesUse the highest-quality asset that meets the published requirements.

Video Attachment

Official
PlacementStatus Attachment
Dimensions1920×1080
Aspect ratio16:9
FormatVideo
File typeMP4, M4V, MOV, WebM
File sizeUp to 99MB
SettingsTranscoded to H.264 MP4; maximum 1300kbps and 120fps
Requirements
  • One video per post
Status Official specification
Reviewed
Source Mastodon Documentation
NotesUse the highest-quality asset that meets the published requirements.

Audio Attachment

Official
PlacementStatus Attachment
Dimensions1200×1200
Aspect ratio1:1
FormatAudio
File typeMP3, OGG, WAV, FLAC, OPUS, AAC, M4A, 3GP
File sizeUp to 99MB
SettingsTranscoded to MP3 V2 VBR, approximately 192kbps
Requirements
  • One audio file per post
Status Official specification
Reviewed
Source Mastodon Documentation
NotesUse the highest-quality asset that meets the published requirements.