Field guide
Rotate a JPEG without losing quality
Quarter-turn JPEG rotation can sometimes rearrange compressed blocks without decoding them. Arbitrary angles always require a new pixel grid and a new encode.
01
Lossless rotation depends on dimensions aligning with the JPEG's minimum coded units. Some tools trim edge pixels when the width or height does not fit those block boundaries.
02
A browser canvas decodes, rotates and encodes again. One high-quality save is usually visually safe, but it is not mathematically lossless.
03
Rotate from the camera original rather than a social-media copy. Each previous encode has already removed detail and introduced ringing that the next encode must preserve.
04
Check EXIF orientation after saving. Pixel rotation plus a stale orientation tag can make another viewer rotate the image a second time.