Why does…? #18: why does a phone get slower when its storage is almost full?

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// WHAT YOU WILL LEARN

Flash memory needs free blocks to write and to shuffle data around; when it is nearly full the phone must erase and move blocks first, so saving and loading take longer.

// LESSON NOTES

Storage almost full — and your phone gets SLOW? Here's why 📱🐢

💾 Phone storage is flash memory. It writes new data into EMPTY spots (pages).
🧱 But it can only ERASE a whole block of pages at once — never just one page.
🔁 Lots of free space? It simply writes into empty pages. Fast!
😩 Nearly full? It has to COPY the good pages somewhere, ERASE the block, then WRITE — again and again. Slow!
📦 Apps also need room for cache, updates and new photos.
✅ Keep about 10–20 % free (on a 128 GB phone that's roughly 13–26 GB).

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