In short
A browser API that stores key-value string data on the user's device with no expiration — persists even after the browser is closed. It is convenient for non-sensitive client preferences and cached UI state, but it should not be treated as a secure place for secrets because JavaScript running on the origin can access it.
How to learn this
- 1Open DevTools' Application tab and manually add/read localStorage values. Inspect at least one real example and note what each important field or stage represents.
- 2Practice `localStorage.setItem`, `getItem` and `removeItem` in the console. Test it with at least one normal case and one edge case so you can explain the behavior confidently.
- 3Learn its 5-10MB size limit and that it's synchronous (can block the main thread).
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