How do you detect memory leaks on iPhone?

Change the view to "Extended Detail" on the instruments panel. This will show you the stack trace of each leaked object after you stop recording and select the leaked object.

You do see calls into the API, but what you are interested in is finding the last method of your application before the API calls, that is where the leak is.

A tip: turn on "gather memory contents" in the leaks view. Seeing the object values should also help finding where the problem is.

You don't want any leaks. 100 leaks is not typical (at least in my apps ;) Typical should be 0.

Note also that the leak tool is not going to show you instances where objects are over-retained and still held on to. Leaks are cases where objects that should have been let go are just hanging around with no-one to clean them up. Over retained objects are validly held onto even though you'd think they should be gone - thus the leak tool cannot point them out, since they are still referred to and there's no way to tell them apart from objects that should still be retained.

To find those, use the memory reporting tool and make sure that memory use goes down fully after you free an object. If you notice something isn't freeing memory, you can start by putting breakpoints in dealloc to see if what you expect to see released is actually getting released.

You need to look for both cases to keep a clean memory footprint.