Free tool No sign-up
Free Mastodon Image Size Guide
Mastodon headers, avatars and post images.
Mastodon previews post images at 16:9 in the timeline. Pick the size, drop in your image, place it and download it at the exact size.
Profile
Cover and banner
Posts
Mastodon post image
1,280 × 720 px · 16:9
Timelines preview images at 16:9. Add a description (alt text) for people using screen readers.
Cropped in your browser: your image isn’t uploaded anywhere.
How it works
How to use the Mastodon Image Size Guide
- 1
Pick the size
Every place an image shows on Mastodon, with the size to upload.
- 2
Add your image
Drag it to place it and zoom to fill the frame. Circles and safe areas show where the network crops.
- 3
Download
Get a JPG or PNG at the exact size, ready to upload.
Mastodon sizes
What to know about Mastodon sizes
Recommended uploads: networks scale images down, never up, so start at least this big.
- 1
Header: 1500 × 500
3:1 at the top of your profile.
- 2
Avatar: 400 × 400
Square, with rounded corners on most apps.
- 3
Posts: 1280 × 720
Timelines preview at 16:9; people can open the full image.
- 4
Add alt text
Many Mastodon users rely on image descriptions. Add one when you post.
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Mastodon Image Size Guide FAQ
Questions, answered.
What size is a Mastodon header?
1500 × 500 pixels, 3:1.
Is the Mastodon image resizer free?
Yes, and it works without signing up. Images are cropped in your browser and never uploaded.
What size should Mastodon post images be?
1280 × 720 matches the timeline preview. Other shapes open in full.
What size is a Mastodon avatar?
400 × 400 pixels.
Do I need alt text on Mastodon?
It’s strongly expected. Descriptions make images accessible to people using screen readers.
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