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What reasons are there for choosing the case-insensitive version of HFS+ when formatting the primary drive partition? Would case-sensitive not always be the best choice?

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See… for a list of programs with HSFX issues and (possible) fixes. – user588 Oct 15 '12 at 9:22
up vote 21 down vote accepted

Use the default (case-insensitive) unless you both a) know what you're doing and b) you absolutely have to. There are several programs (Norton Antivirus comes to mind) that won't work properly on a case-sensitive file system.

HFS is, by default, case-insensitive but case-preserving (i.e. it doesn't care what you type for comparison purposes, but it will remember what you type).

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One or other can break applications, case-insensitive is the default however. If you've been using case-insensitive without issues then there are no guarantees that a transition to case-sensitive will go well. Here's one example from the apple support pages:

...don’t assume your third-party software solutions work correctly with case sensitivity. Important: Case-sensitive names do not ignore Unicode ignorable characters. This means that a single directory can have several names that are considered equivalent using Unicode comparison rules, but they are considered distinct on a case-sensitive HFSX volume.

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So what's the standard then? Case-insensitive? – Ian C. Feb 9 '11 at 0:30
Case-insensitive is standard, and is almost always the better option. – CajunLuke Feb 9 '11 at 0:34
@CajunLuke: Thanks! – Ian C. Feb 9 '11 at 0:41

There are some significant applications that will not work correctly with case sensitive. And there's really no reason to do it. I'm assuming since you're asking that you really don't have a reason to do it. You're definitely better off not doing it unless you have a specific reason, and don't care that many applications don't work right with it.

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There is a good reason to choose a case sensitive file system. If you are concerned by the quality and the security of the applications you run you might be interested by any early mechanism which may discriminate badly programmed applications.

An application which at one time create a file named conf and later try to open the same file with the name CONF is at least poorly written. This is just plain bad programming practice. This kind of application is filled with vulnerabilities with the same average probability all over its code length. This is a dangerous application.

This dangerous application will most probably crash on a case sensitive file system.

This dangerous application will not crash on a case insensitive file system.

(Some applications will crash on both, but we are not highly motivated to sort out these ones.)

Hence a case sensitive file system may be considered as a good tool to early detect and block poorly programmed applications.

On the other hand, this level of programming quality control is far from sufficient to ensure that you don't have any other vulnerability.

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So basically you are saying that as a developer/tester one should use a case sensitive filesystem, and as a mere user a case insensitive one? – patrix May 20 '13 at 17:54
→ Patrix: I would advise every user to use case sensitive filesystem. No need to discriminate users. Better fight poorly written applications which are the roots of all security vulnerabilities. – daniel Azuelos May 20 '13 at 19:32
It doesn't help the user if he needs to use an application which expects filesystems to be case insensitive (Adobe still has issues there for instance). – patrix May 20 '13 at 19:33
→ Patrix: how right you are "Adobe still has issues there". Meanwhile, Adobe is sometimes able to make applications which are cleanly programmed and which run without a glitch on nearly every OS on the marketplace (Adobe reader). – daniel Azuelos May 20 '13 at 19:41

One good reason to use case sensitive file system is using git repositories. Syncing them to the repo causes problems again and again, if not using case.

But I suggest adding another partition using HFS+ formatted case sensitive for such an application and link the directories you need to that partition. My system partition is still case insensitive not because I kwow why but just because I'm afraid.

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Apparently there's nothing to fear. OS X will run fine on case-sensitive HFS+. Though some applications may not. And I agree: git is a very good reason to do this. – Ian C. Apr 14 at 15:26

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