What's the difference between AppData and Application Data folders? (And why have both?)

Question:

I use Vista which I find far more difficult to navigate than the XP used
formerly. For some reason all my files seem to have duplicated themselves and I
cannot access them. For example I have two folders entitled application data
and another app data. I can access one but when I try to access the other I am
told that the folder is inaccessible and access is denied. Did I perhaps
inadvertently initiate a share or something equally stupid?

Nope, nothing you did at all, stupid or otherwise.

This is part of some kind of redesign that Microsoft initiated in Windows
Vista that folks just now upgrading to Windows 7 are encountering as well.

And I agree, it’s confusing. I can take some guesses as to why they both
exist, but first let’s look at exactly what they are, and perhaps more
importantly, what they are not.

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Application Data and AppData are almost the same thing.

AppData is the intended location for user-specific data that applications might want to keep. For example, if your machine has two users, “John” and “Mary”, a program might save different settings or files depending on who’s logged in and using the machine by placing those settings somewhere within the AppData folder for that user.

Within AppData, you’ll find a couple of additional folders, most notably “Local” and “Roaming”. “Roaming” folders are designed for networks that support what are called “Roaming Profiles” – a scenario where your documents and setting are available to you no matter what computer you log into in your corporate network, as long as you login with your unique username. “Local” are then settings that are only local to that specific machine.

“The files are not duplicated, they’re simply in a single folder that can be accessed via different names.”

It feels like overkill, since the majority of consumers

have only one login account on their machine
have never heard of, much less used, “Roaming Profiles”

They’re both artifacts of Windows being designed as a multi-user operating system also targeted at large corporate installations.

“Application Data” is what you would find in Windows XP.

In Windows Vista and Windows 7, “Application Data” is actually an alias or a synonym (in geekier terms, a “hard link”) to your “AppData/Roaming” folder.

You can actually prove this yourself. In a Windows Command prompt, you can write to the “Application Data” folder. This example simply echos the string “foo” into a text file “foo.txt” in the Application Data folder:

C:\Users\LeoN>echo foo >"Application Data\foo.txt"

And now, if we look at the AppData\Roaming folder:

C:\Users\LeoN>dir AppData\Roaming
 Volume in drive C has no label.
 Volume Serial Number is 50FF-9FCF

 Directory of C:\Users\LeoN\AppData\Roaming
01/10/2010  10:17 AM    <DIR>         .
01/10/2010  10:17 AM    <DIR>         ..
01/10/2010  10:17 AM                 6 foo.txt
08/26/2009  08:03 PM    <DIR>         Identities
11/02/2006  07:06 AM    <DIR>         Media Center Programs
08/27/2009  07:56 AM    <DIR>         Parallels
               1 File(s)              6 bytes
               5 Dir(s)  10,194,100,224 bytes free

You can see that even though we created the file in “Application Data” it appeared in “AppData\Roaming”.

In fact, there are several aliases that were created as a result of some reorganization in Windows Vista: “Documents And Settings” became “Users”, “My Documents” became “Documents”, and others.

The bottom line is that even though the files might appear as if they’re in two locations, they’re not. The files are not duplicated, they’re simply in a single folder that can be accessed via different names.

Now, the other question: why?

I can only speculate.

Why the reorganization? Probably to more cleanly allow things like Roaming Profiles to work, and support a cleaner division between information local to a machine or portable across multiple machines when Roaming Profiles are used. In the case of the average consumer there’s no clear benefit or difference. (There may well be other reasons as well.)

Why different names? As I look at the new names, they share on common characteristic: they no longer have spaces in them. My belief is that they took advantage of the situation to remove spaces from within names, since it’s common for people – and programs – to get confused by spaces in file and folder names. To the average consumer I consider this a pretty significant usability improvement, as there’s no longer a concern about whether or not you need to worry about things like quotes around “Documents and Settings” when plain old Users will do.

Why the aliases? In a word, compatibility. There are programs that assume “Documents and Settings”, rather than using the system provided functions to ask “where should I put user data?”. Removing those names would probably break a number of applications.

Why the draconian permissions on those old names? To “encourage” (aka “force”) users and future applications to move to the new/correct names.

So what it all comes down to is this: it’s a reorganization that for the most part shouldn’t really impact the average user.

Or to put it another, less useful way: it is what it is.

11 comments on “What's the difference between AppData and Application Data folders? (And why have both?)”

could the removal of the spaces have soething to do with Unix compatibility. I had to remove the spaces from my filenames when I migrated my web site to a Linux server so I imagine there would be a problem with spaces on a mixed Unix/Windows network.

It’s possible, but Unix/Linux file systems support spaces as well.

12-Jan-2010

Probably a good answer- technically, but a bit too technical for the average reader. If one uses the ‘run command prompt’ he/she is probably aware of the answer.(not to be critical)-Love Leo!

Another question on Application Data folders, is when I try to open file, met with Access Denied”. The file in question is in Windows 7 Backup.

That’s correct – you should access it via the AppData folder instead.

14-Jan-2010

Thanks for the answer because it clears up for me the “why” Microsoft has made changes and especially why the old XP addresses for files has drastically changed and I have had trouble learning the “system” in locating files and folders in windows7. Now I can forget about trying to locate My Documents and such in the new os and can concentrate on learning how to navigate using the new look.

Yes, I think that’s right about why the linkage is there, I have some older programs which try to put the files in Document and Settings. Sometimes it gets confusing because certain programs can see these links and it gets messy.

One free tool I probably use as often as email is Everything – quick and easy way to find your files on any of your disks (and I have almost 8 TB on my desktop). It’s super fast and you only have to remember the file name, or part of it. I uninstalled Google desktop search and turned off the Microsoft thingy after I experimented with Everything. Download at http://www.voidtools.com/

[[Sorry if this is a duplicate comment. I’m repeating it because I received a message that either I have Javascript disabled or am using some technique that comment spammers use. I got an XSS warning from noscript (I use Firefox), but after looking at the console, I saw that was because I disallowed pugetsoundsoftware.com. BTW – I get dozens of messages like Warning: The ‘charCode’ property of a keydown event should not be used. The value is meaningless.; also repeated with keyup event. There are a few other warnings too. :)]]

Is not one (or both?) of these a junction point? See http://en.wikipedia.org/wiki/Junction_point. I don’t know much about them, except that they have a lot to answer for.

Yes, I believe one or the other is implemented as a Junction or something similar to a Junction

15-Jan-2010

Reading your article made an old lady very happy. I lost all my photos of a dream holiday for which I have worked 42 years simply because I thought everything was duplicated. Now if you could explain to me what common files are, perhaps I can make some progress on this new-fangled machine. Thank you for your ‘reasonably’ simply explanation. I am a learner and a technophobe but am trying very hard to understand, rather than just USING my computer. Thank you so much, young man. Regards Pat

@Pat
Common or shared files are files stored in a folder which is shared among all users of that computer. In Windows 7, it is the c:\Users\Public\Documents\ folder (or something similar in other versions of Windows). When there are more than one user registered on the computer, each user can only see what is in their Documents folder plus the contents of that common or folder.

Mark J, it was very kind of you to try to help me. I have vista and am the only user but I also have to be the administrator, (Apparently!) Does this mean that the common files (C:\Prog Files\Common Files) viewable depend upon whether I log on as Pat or Pat Administrator? Am I being thick or possibly trying too hard to understand? I really do appreciate you bothering to answer my query. Thank you again

@Pat
Actually, I explained another kind of common files. The c:\program files\common are different. This is a folder for program components which are share amongst more than one program. These are files that are maintained by the system and the programs that install them. As the old saying goes there are no user serviceable parts inside. But if you do need to view them, they should be visible from any administrator account. You may have to set your Windows Explorer to view system and hidden files in order to see them.
If you are looking for lost photos you might try the advice in this article:
http://ask-leo.com/how_do_i_recover_my_lost_photos_on_my_hard_disk.html

What's the difference between AppData and Application Data folders? (And why have both?)

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