Resize images for Mastodon- avatar 400×400, header 1500×500, media attachment 1920×1080, custom emoji 50×50+. Free online tool.
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All recommended Mastodon image dimensions for 2026. Upload at these exact sizes to avoid any quality loss from platform-side scaling.
| Type | Width × Height | Aspect Ratio | Notes |
|---|---|---|---|
| Profile Avatar | 400 × 400 px | 1:1 | Displayed as circle or rounded square |
| Header Image | 1500 × 500 px | 3:1 | Profile banner (3:1 ratio) |
| Media Attachment | 1920 × 1080 px | 16:9 | Max dimensions, 16 MB limit |
| Custom Emoji | 50 × 50 px | 1:1 | Minimum 50×50, max 50 KB |
Open ResizePack, drop your image and select the Mastodon preset - Avatar, Header, Media Attachment or Custom Emoji.
For header images, use CropRatio at 3:1 first to frame your composition, then resize to 1500×500. For avatars, center your subject since some instances display them as circles.
Download and upload to your Mastodon instance via Preferences > Profile. Media attachments are uploaded directly in the compose window when creating a new post.
Ready to resize?
Use Batch Resize for batch resizing with social media presets, or Crop & Ratio to crop to the exact aspect ratio first.
The recommended Mastodon avatar size is 400×400 px. Different Mastodon instances may display avatars as circles or rounded squares depending on their theme. Upload a square image with the subject centered to look good in both display styles.
The recommended Mastodon header (banner) size is 1500×500 px (3:1 ratio). This is the same ratio as Twitter headers. Keep important content centered since mobile apps may crop the edges. Maximum file size is typically 2 MB.
Mastodon supports media attachments up to 1920×1080 px with a maximum file size of 16 MB for images. Supported formats include JPG, PNG, GIF, and WebP. Images larger than the limit are automatically downscaled by the server.
Mastodon custom emojis must be at least 50×50 px. The maximum file size is 50 KB. PNG format with transparency is recommended. Custom emojis are added by instance administrators and can be used by all members of that instance.
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Need dimensions for every platform in one place? Read our complete 2026 cheat sheet- every network, every format, updated for this year.
Social Media Image Sizes 2026