Why is my phone slow all of a sudden?

Most common: a recent OS update is still re-indexing, storage is over 85% full (iOS / Android both throttle), the battery has aged past 80% capacity (CPU throttles to protect runtime), or a background app is leaking.

Does clearing cache speed up a phone?

Marginally and briefly. App cache fills back up within hours of normal use. Free storage and battery health matter far more than cache clearing.

Wizard / W05

My phone is slow.

Press start. We benchmark CPU, GPU, storage, memory, and network and tell you whether the chip, the storage, or the radios are dragging you down.

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Storage cleanup

iOS: Settings → General → iPhone Storage. Android: Settings → Storage. Anything over 85% full slows everything. Offload unused apps, clear caches, delete giant photo / video files.
Battery health

iOS: Settings → Battery → Battery Health. Anything under 80% maximum capacity triggers OS-level CPU throttling. £89 replacement at Apple. Android: install AccuBattery for a similar estimate.
Restart cycle

If you can't remember when you last fully powered down, do it now. 30-day uptime is normal but causes drift; restart resolves a surprising number of slowness reports.

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