Storage

The lag caused by a nearly full storage is the most easily overlooked kind: it doesn't come with heat, a restart won't fix it, and the only signal is the progress bar in Settings → General → iPhone Storage. The key to understanding it is one metaphor — free space is the system's scratch paper. The fuller the desk, the longer the cleanup before any real work.

This section covers:

1. The mechanism — why everything slows down once free space drops below 10%, and why even heat goes up
2. The self-check — where to look, which numbers matter, and how to tell if storage is the real cause of your lag
3. The three-step cleanup — photos and videos (the biggest chunk), WeChat cache (the most hidden), and apps you installed and forgot (the quickest), ordered by payoff

Start with Why Storage Space Affects Speed — a storage checkup takes about ten minutes.