I have a few apps on my iPhone, and would like to sync them with iTunes without erasing them from my phone. Is this possible without downloading them all again?
If the apps were not downloaded from iTunes in your system, while syncing you should be asked if you would like to transfer your purchases to iTunes, say yes at this prompt. Alternatively, there should be an option in iTunes for transferring purchases.
I just tested this out by alt clicking iTunes, creating a new library, and connecting my iPod. This happens when you try to sync with a library that is not the same as the one your iPod is associated with.
Afterwards, you can sync, and everything will be erased and rewritten to the iPod.
I'm not sure why Apple makes this so confusing. The only reason I can come up with is that they want people to have to repurchase stuff but that seems a little over the top even from Apple.
From an Apple.SO answer:
I had this same issue after I recreated my iTunes library. This may be totally off because it was about a month ago, but I think I did this:
protected by studiohack♦ Apr 15 '11 at 2:57
Thank you for your interest in this question.
Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.
Would you like to answer one of these unanswered questions instead?