Panorama size and format requirements

Requirement	Value
Format	JPEG, PNG or WebP (checked from the file contents, not the extension)
Shape	2:1 width to height (small tolerance)
Width	at least 2048 px, up to 16384 px (8192 × 4096 recommended)
File size	up to 50 MB

If we reject an image the message says why, for example "must be 2:1". Re-export your stitched panorama without cropping. We can verify the shape but not that the picture is truly spherical, so check it in Preview.