Can I safely rotate JPEG images on my MacBook or would this be lossy?


Using Preview.app, the rotation applied is not lossless. You need to use a special tool that will either add an EXIF rotation header (which is then applied only on display) or simply keeps the encoding coefficients constant, but shifts them accordingly. One tool that supports this that has a UI is Xee, on the commandline you could use jpegtran or imagemagick.


I would of thought that any differences would be negligible however:

Create a copy of your picture then rotate that, compare file sizes / image quality after.

JPEG is already a lossy compression format in either case.

  • This does not answer the question, I guess.
    – oa-
    Sep 21 '17 at 7:35

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