Bluesky Image Size in 2026: The 2 MB Limit, Aspect Ratios, 10-Photo Posts and Alt Text

A Bluesky image can be any size up to 2 MB per file, and since April 2026 the app displays photos at up to 4000 pixels, so file size, not pixel size, is the limit you will actually hit. Bluesky publishes no recommended dimensions: 1080x1350 (4:5) for portrait, 1080x1080 for square and 1200x675 (16:9) for landscape are the sizes most guides suggest, and Bluesky does not require any particular shape. Since June 2026 a post can hold up to 10 photos.

What are the Bluesky image limits in 2026?

The 2 MB figure comes straight from Bluesky's open protocol, which sets a maximum of 2,000,000 bytes per image. That is slightly less than some computers mean by 2 MB, so aim for 1.9 MB or less. TechCrunch reported the jump from 1 MB, and the move to 4000-pixel rendering, on 23 April 2026. Articles that still say 1 MB or four images per post were written before those updates.

What size should a Bluesky image be?

Bluesky does not publish a recommended size and does not lock you into a ratio. These are the sizes 2026 guides suggest; they are guidance, not Bluesky rules.

Because Bluesky now displays up to 4000 pixels, a larger file is not wasted the way it is on Instagram, which scales everything down to 1080 wide. A 2160x2700 version of a 4:5 post can look sharper on large screens, as long as it still fits in 2 MB. For photos and gradients that usually means saving as JPEG; flat graphics with large areas of one colour often fit as PNG.

How does Bluesky handle aspect ratios and cropping?

Each image in a Bluesky post can carry its own aspect ratio, a width and a height stored with the post, so apps can lay the image out at the right shape before it loads. TechCrunch reported in April 2026 that Bluesky's new carousel handles mixed aspect ratios without cropping them, and since June 2026 any post with five or more photos is shown as a swipeable carousel. So, unlike on Instagram, mixing shapes in one post should not cost you a crop.

What Bluesky does not document is how far a single very tall or very wide image is trimmed in the feed before someone taps it, or how the grid used for two to four photos crops each one. No crop limits were published as of October 2026, and third-party Bluesky apps can lay images out differently. Keep important text away from the very top and bottom of tall images, and check the preview before you post.

How do you add alt text to a Bluesky image?

Alt text is optional in Bluesky's protocol, which sets no length limit. The official app allows up to 2,000 characters per image; other apps can set different limits. If you want a reminder, turn on "Require alt text before posting" under Settings, Accessibility, and the app will ask for a description on every image.

For a designed graphic such as a quote card, a statistic or a carousel slide, the alt text should include the words on the image. Screen readers cannot read text that is part of a picture, so without alt text the whole message is lost to anyone using one. Write it the way you would read the slide aloud: the headline first, then the supporting line, then anything else that matters, such as a source or a date. For a 10-photo post, that means 10 descriptions, so draft them alongside the copy rather than at the last minute.

How do you get a design under the 2 MB limit?

Design at the size you want first: a custom canvas in Canva or Figma, or the size in the first line of a Claude Design prompt ("Design a 1080x1350 post..."); the social post prompts include ready-made examples. Claude Design can download a single artboard as a PNG at 1x or 2x.

Then check the file size, because a 2x PNG of a photo-heavy design can easily pass 2 MB. Renda, which renders HTML exports from Claude Design and other AI tools into one PNG per slide, has no Bluesky preset: Auto-detect renders the design's own canvas at 2x, and the output is always PNG, with no compression step. So run any file over 2 MB through a free converter such as Squoosh: choose JPEG (MozJPEG) and lower the quality until the file is under about 1.9 MB, keeping the full resolution if you can.

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