Free tool
Mastodon image resizer
Resize an image to the right Mastodon size and save it as JPEG or PNG. Everything happens in your browser: the image never leaves your device.
Preview
Choose an image to see it here.
Mastodon character limit
A Mastodon post can have up to 500 characters. That is the limit on mastodon.social. Other Mastodon servers can set their own.
How this counter counts
Every link counts as 23 characters however long it is, and a mention of someone on another server counts as just @user.
Mastodon image sizes
| Image | Size | Notes |
|---|---|---|
| Avatar | 400×400 | Larger images are reduced to this size. WEBP, PNG, GIF or JPG, up to 2 MB. |
| Header | 1500×500 | Larger images are reduced to this size. WEBP, PNG, GIF or JPG, up to 2 MB. |
| Post image | Reduced to 8.3 megapixels | Up to 16 MB and four images per post. Your server’s limits may differ. |
Sources, checked November 2026: Mastodon docs: profile, Mastodon docs: posting
Also for Mastodon: the free Mastodon character counter.
Schedule Mastodon posts
PostDelegate publishes to Mastodon today. Plan posts on one calendar and schedule them with the Mastodon scheduler, or have your assistant draft them: Claude · ChatGPT · Claude Code · Codex · Cursor · Gemini CLI. Start your 7-day free trial, no card needed.
Questions
Is my image uploaded anywhere?
Where do these Mastodon sizes come from?
What is the difference between cover and contain?
More free image resizers
Instagram · LinkedIn · YouTube · X · Bluesky · Pinterest · Twitch · Dribbble
Or check every network at once with the image resizer, and see all free tools.
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