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I have 2 JPEG files that appear the same, i.e. the same pixel data, same dimensions, but one of them is a much larger file size.

The download time for these files is important to my client, so I need to determine where the larger one came from and why it is bigger.

The larger file has an Exif comment that says "AppleMark". What software might add this in?

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Do you use an importer program or just drag & drop from a media card? I have read a few times that the "AppleMark" is placed in images that have been altered on import (auto rotation being the most common alteration on import). – nerdwaller Aug 9 '13 at 15:12
They are on a customer's machine, so I don't know all of the software they use. – Liam Aug 9 '13 at 15:34

I found the AppleMark in several of my JPEGs and found your question by searching on the Internet for the phrase 'AppleMark'. it appears in my iPhone Library Thumbnail files.It also appears in files created by a program called MP Navigator. I have also seen it in files created by Preview. I suspect that it is an artifact of an Apple JPEG compression library.

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