Bluesky Safe Zone Checker (Free — Overlay Your Own Frame)

Bluesky does not stretch or squash images — instead it center-crops anything taller than roughly a 2:1 ratio to fit the feed column. That means a portrait or near-square image has its top and bottom bands hidden in the timeline preview; viewers only see the full image after tapping through. The cropped bands are still in your file, just out of view until the tap. Knowing where those bands fall lets you keep important content — faces, product shots, text overlays — in the visible strip rather than accidentally buried at an edge.

The recommended workaround is to export at 1200 × 675 px (16:9 landscape) for designed graphics, because a wide image is never taller than the crop threshold and therefore shows in full. When you do need a taller format, use this overlay to confirm your focal point lands in the centre band that survives the feed preview.

Two secondary overlays complete the picture. When an image carries alt text, Bluesky renders a small "ALT" chip in the bottom-left corner of the feed image — covering a modest but real patch of your image. That chip is a good sign (accessible content), but it’s worth checking it doesn’t sit directly over a logo, face, or important caption element. Position those slightly higher or toward the right half of the frame to stay clear.

In a multi-image post, Bluesky arranges the images in a grid and crops each tile closer to a 1:1 thumbnail. That trims more from the top and bottom than a single-image preview, so any composition you’ve built for a wide single-image view may lose even more edge content in the grid layout. The multi-image overlay shows that additional band so you can plan for both scenarios when creating a set of images meant to be posted together.

The readout under the preview reports one thing only: how much of the total frame each overlay zone covers. That number comes purely from the rectangle geometry — it is not looking at your image, and it makes no claim about whether your subject is cropped, because no browser tool can know what the subject of your image is without guessing. We would rather show you an honest map of where the feed cuts than fabricate a confident-sounding "subject hidden" score.

Use the legend toggles to isolate a single zone when fine-tuning placement, and read the per-zone notes for what each region represents. The positions are transcribed from documented Bluesky feed behaviour, but Bluesky varies its crop logic by client, app version, and aspect ratio — so treat the overlay as a strong guide and leave yourself a margin at every edge.