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By default, CrashPlan backs up your User folder, which contains the AppData folder for your Windows computer. Files in this folder update quickly. Consequently, your backup may not be reaching 100% if this folder is kept in your backup set. This article explains what the AppData folder is so that you can determine whether you want to keep it in your file selection.
What is the AppData folder?
AppData is a hidden folder located in C:\Users\YourUsername\AppData\. The AppData folder contains custom settings and other information needed by applications. For example, you might find the following in your AppData folder:
- Web browser bookmarks and cache
- CrashPlan's configuration files
- Temporary files
CrashPlan and AppData
Certain files inside AppData can fail to back up with CrashPlan. When this happens, your email reports show less than 100% backed up, and CrashPlan's History log displays the message "unable to backup X files." This happens because the files in this folder:
- are open and locked down by the application that created them
- were not created with the correct permissions for CrashPlan to back them up
This is rarely a cause for concern--files that fail to back up from the AppData folder are typically temp files that do not need to be restored. CrashPlan is designed to protect your user files (think Desktop, Documents, Pictures, etc.), not your entire operating system and applications.
Examples of AppData files that commonly fail to back up
C:\Users\YourUsername\AppData\Local\Microsoft\Windows\Notifications\WPNPRMRY.tmp C:\Users\YourUsername\AppData\Local\Microsoft\Windows\UsrClass.dat.LOG1 C:\Users\YourUsername\AppData\Local\Microsoft\Windows\UsrClass.dat.LOG2 C:\Users\YourUsername\AppData\Local\Microsoft\Windows\WebCache\WebCacheV01.dat C:\Users\YourUsername\AppData\Roaming\Skype\your.skypename\main.lock C:\Users\YourUsername\AppData\Local\Google\Drive\lockfile C:\Users\YourUsername\AppData\Local\Microsoft\Internet Explorer\Recovery\High\Active*.dat C:\Users\YourUsername\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>.default\parent.lock C:\Users\YourUsername\AppData\Local\Google\Chrome\User Data\Default\Current Session C:\Users\YourUsername\AppData\Local\Google\Chrome\User Data\Default\Current Tabs C:\Users\YourUsername\AppData\Local\Google\Chrome\User Data\lockfile
Should I just remove the AppData folder from my backup?
It's up to you. Because most applications only store their configurations settings, not files you create, in this folder, it's often not important to back it up. However, there are exceptions to that rule--most notably older versions of Outlook (see below).
If you decide to change your file selection to remove the AppData folder, there are a few things to keep in mind:
- When changing your file selection, check Show hidden files to reveal the AppData folder
- Expand the AppData folder and check for any subfolders you may want to continue backing up (e.g. your web browser's bookmarks or your Outlook PST files)
- If you're not sure what you need, leave AppData selected and troubleshoot the unable to backup X files issue if you see files within AppData failing to back up
Exception to the rule: Outlook
Versions of Outlook prior to Outlook 2010 stored your PST files (a.k.a. Personal Folders, commonly used for archiving mail) in: C:\Users\YourUsername\AppData\Local\Microsoft\Outlook\
However, later versions store PST files in C:\Users\YourUsername\Documents\Outlook Files\, which CrashPlan backs up with the rest of your Documents folder.
If you're not sure where your Outlook PSTs are located, see this article from Microsoft: "How to locate, move, or back up your personal folders (.pst) file in Outlook"