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I can't find this information documented anywhere. What filesystem do iOS devices use? Did Apple stick with HFS+? Is it different between devices and iOS versions?

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up vote 10 down vote accepted

The other answer seems to be correct about the file system being HFSX, but on being case-insensitive (other answer since edited to correct), I found that not to be the case in the book Mac OS X and iOS Internals. On page 23 it says:

In iOS, being the case sensitive HFSX by default, case is not only preserved, but allows for multiple files to have the same name, albeit with a different case. Naturally, case sensitivity means typos produce a totally different command or file reference, often a wrong one. [emphasis above is mine]

Since that didn't agree with the other answer, I sought confirmation. I loaded a sample iOS project I was working on and changed the name of the database to only differ by case. After running the app on my iPad mini (iOS 6.1) to re-create the database, I went into iTunes and looked at the files under File Sharing for the application. Here's what I saw:

Screen shot from iTunes File Sharing demonstrating two file names with identical names differing only by case

So, it would appear Mac OS X and iOS Internals is correct: case is preserved and allows for multiple files to have the same name.

Interestingly, when I selected both files in iTunes' File Sharing and clicked "Save to..." my desktop, I did not get any warning. iTunes apparently "saved" both files to my desktop, but only the initial-uppercase version survived (presumably overwriting the initial-lowercase version of the file.)

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My error I misread the quote and missed the "in" –  Mark Feb 27 '13 at 14:22
    
@Mark No problem. What's more interesting is the behaviour where it preserves both versions .. something I wouldn't have ended up reading about & testing if not for your innocent error :-) –  Chris W. Rea Feb 27 '13 at 14:24
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iOS indeed uses HFSX (HFS+ , case sensitive). You can also use the HFSleuth tool from the Mac OS X/iOS Internals website, to prove this, and delve deeper into the filesystem structures.

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I can't see any definitve Apple documents but books quoted in these Stack Overflow questions and this and this book say HFSX (ie case sensitive HFS+) which is not the same as the default for OSX.

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