12

I can't find this information documented anywhere.

What filesystems do iOS devices use?

Did Apple stick with HFS+?

Is it different between devices and iOS versions?

6

As of iOS 10.3 (March 2017) - APFS/Apple File System is now the file system being used.

Previous to iOS 10.3 HFS+ was being used.

APFS will add improved support for solid-state drives and encryption improvements - things that were not a priority 20 years ago when HFS+ was introduced.

  • APFS is used by the first developer beta version of iOS 10.3; it may be used in the general release of iOS 10.3, but we don't know that yet. – Gordon Davisson Jan 29 '17 at 22:38
18

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.)


* 2017 Update to Apple File System (APFS):

As of iOS 10.3, released on March 27, 2017, iOS now uses the new Apple File System (APFS), said to be "optimized for flash and solid-state drive storage, with a primary focus on encryption."

APFS was announced at WWDC 2016 and there is a WWDC video titled Introducing Apple File System, and an Apple File System Guide for developers. The features section of the guide may be of specific interest.

  • 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
3

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.

2

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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