iOS 5 Cleans Out Caches & Tmp Folder, Might Wipe Out App Data

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Apple has just released iOS 5 and millions of iPhone, iPad and iPod Touch users around the world are updating their devices to enjoy new features like iCloud and iMessage. But developers warn that some application data might be compromised by the new iOS version.

Instapaper creator Marco Arment writes about a potential issue with how some iOS apps store data on the iPhone, iPad and iPod Touch. Every iOS application stores user data in a certain folder, he says, which are synchronized via iTunes when users plug in to their computers. Some app developers prefer to store data within the Caches and Tmp folder to avoid slowing down iTunes syncing. However, this might prove to be a problem, given a new cleanup policy being implemented in iOS 5.

In gist, iOS 5 now cleans up the contents of Caches and Tmp when device storage is low. Apple has issued an advisory to developers that this new policy is due to iCloud syncing user data with Apple’s servers, which means there is no longer the need to synchronize via iTunes.

This will be a concern with users who have apps that save and cache data for offline consumption, which is one of the main highlights of apps like Instapaper. Users have reported their saved content and other user data being deleted because of this “Cleaning” activity by iOS 5. Developers are now trying to convince Apple to implement data storage that is not synced with iCloud, but not cleaned out unless the user explicitly decides to do so. This might be useful in saving bandwidth, but making sure user data is not inexplicably removed.

There needs to be a file storage location that behaves the way Caches did before iOS 5: it’s not backed up to iTunes or iCloud, it’s not synced, but it’s also never deleted unless the app is deleted.

Users might not notice the issue until Apple clears out their cached content, so it’s mostly a concern that developers are trying to work around at this point. But if you use apps like Instapaper or certain ebook readers, offline magazines, mapping applications, podcast clients and the like, you might want to watch out for lost data if you run low on space.