Bluesky image sizes
| Use | Size (px) | Ratio | Notes |
|---|---|---|---|
| Post image | Not fixed | Any | The official app resizes post images to at most 4,000 px on the longest side and 2 MB. The app composer allows up to 10 images through the newer gallery embed; the older images embed, still used by many API clients, allows 4. Since app version 1.123 (June 2026), posts with 5 or more images show as a swipeable carousel. |
| Avatar | 1000 × 1000 | 1:1 | PNG or JPEG up to 1 MB per the profile lexicon. 1000x1000 is Hootsuite's recommendation. |
| Banner | 3000 × 1000 | 3:1 | PNG or JPEG up to 1 MB per the profile lexicon. Size recommended by Hootsuite. |
Which size to use
Profile images have firm file limits: the avatar and the banner must each be PNG or JPEG up to 1 MB, per Bluesky’s profile lexicon. Hootsuite recommends 1000 × 1000 for the avatar and 3000 × 1000 (3:1) for the banner.
Post images have no fixed ratio. The official app resizes them to at most 4,000 pixels on the longest side and 2 MB. The current app can attach up to 10 images, or 4 through the older embed many API clients still use, and since app version 1.123 in June 2026, posts with five or more images show as a swipeable carousel.
Because any ratio works for posts, the general square, portrait and landscape shapes in the size menu are simply good starting points, not Bluesky rules.
Bluesky video limits
The resizer handles still images. For video, these are the limits to plan around.
| Use | Max length | Max file size | Ratio | Notes |
|---|---|---|---|---|
| Video post | 10 minutes | 300 MB | Not specified | Bluesky announced 10 minutes and 300 MB on August 25, 2026. The app accepts MP4, MPEG, WebM, MOV and GIF files. A video can have up to 20 WebVTT caption files. |
Tips for Bluesky images
- Save the banner as JPG and check that the file is under 1 MB; simple, flat designs compress best.
- Write alt text for every image. The app allows up to 2,000 characters.
- Give every image in a multi-image post the same shape so the carousel looks tidy.
Schedule Bluesky images with Postocial
Schedule Bluesky posts with images in Postocial: add images from the media library, write alt text and a 300-character post, and pick a time. On Premium and higher plans, replies come into the unified inbox.
See how Postocial works with Bluesky.
Sources
The Bluesky sizes on this page come from these pages. Where a network publishes no size of its own, we say whose recommendation it is. Researched on . Networks change their limits without notice, so check the official pages before a big launch.
- Bluesky lexicon: post
- Bluesky lexicon: profile
- Bluesky lexicon: image embed
- Bluesky lexicon: gallery embed
- Bluesky lexicon: video embed
- Bluesky lexicon: rich text facets
- Bluesky app source: constants
- AT Protocol source: handle rules
- AT Protocol: handle specification
- Engadget: Bluesky supports 10-minute videos
- GIGAZINE: Bluesky photo carousels
- Hootsuite: social media image sizes guide