Mastodon Image Sizes & Presets
Mastodon uses 400x400 avatars and 1500x500 headers, and it downscales large post images for delivery across federated instances. Because each instance can set limits, the safest workflow is to crop to the expected dimensions and compress before upload. FastEdit prepares profile images, post images, and short animated media locally in your browser.
Pick this preset, drop your file, and FastEdit starts from the Mastodon Avatar dimensions, format, and file-size target.
Mastodon Image Size Cheat Sheet
Avatar
400x400 PNG / JPEG / GIF Max 2 MB
Profile picture shown as a circle in most themes. Animated GIFs are supported on most instances. Keep subjects centered.
Open Mastodon Avatar preset →Header
1500x500 PNG / JPEG / GIF Max 2 MB
Profile page banner at 3:1 ratio. Displayed behind the avatar and bio. Animated headers (GIF) are supported on most instances.
Open Mastodon Header preset →Post Image
3840x2160 PNG / JPEG / WEBP / AVIF Max 16 MB
Large 16:9 attachment size that stays within Mastodon's image downscale target. Useful for screenshots, artwork, and announcement graphics.
Animated GIFV Source
1280x720 GIF / MP4 / WebM Max 16 MB
Safe animated-media target for looping GIF-style posts. FastEdit can trim, resize, and export short clips before upload.
Before you upload
- Most Mastodon instances support animated GIF avatars and headers: check your instance settings for specific limits.
- Avatar images are typically displayed as circles, matching the same style as X/Twitter and other social platforms.
- Header images may be cropped differently depending on the Mastodon web client or app being used: keep content centered.
- Profile image limits can vary by instance: 2 MB is a safe maximum for avatars and headers on most servers.
- For post attachments, add alt text in Mastodon after upload. FastEdit prepares the file; Mastodon stores the media description.