Mastodon image sizes
Avatar
1:1400×400
Displayed circular or rounded depending on theme.
Verified July 20, 2026
Profile header
3:11500×500
3:1. Instance themes may crop differently.
Verified July 20, 2026
Post image
16:91280×720
16:9 is common; taller images also work.
Verified July 20, 2026