Clear your iPhone's cache, and you could see your device running faster. Clearing your iPhone's cache is easy maintenance that you should make a regular priority, as a cluttered cache could be the reason your iPhone is slow. You can clear up space on your iPhone's cache by manually deleting information from your individual apps and browser, or by deleting and reloading apps to automatically clear the cache. Here's an easy step-by-step process to clear your cache from Safari and third-party apps.