Glossary · Junk files
What are junk files on an Android phone?
Short answer
Junk files are data that apps and the system create for short-term use and no longer need: app caches, leftover APK installers, temporary downloads, log files and stale thumbnails. Deleting them is safe, but caches rebuild as you use apps, so the space they free is often temporary. Photos and videos usually take far more room.
Last updated
What counts as junk on Android?
| Type | Where it comes from | Safe to delete? | Comes back? |
|---|---|---|---|
| App cache | Images and data apps store to load faster | Yes | Yes, as you use the app |
| APK files | Installers downloaded outside Google Play | Yes, once installed | No |
| Temporary files | Unfinished downloads, crash logs | Yes | Occasionally |
| Thumbnail cache | Small previews the gallery generates | Yes | Yes, on next scroll |
| Empty folders | Left by uninstalled apps | Yes | No |
How do I clear junk files for free?
- Open Files by Google and tap Clean. Its top card, often labelled Junk files, lists temporary files and app caches; tap Clean and confirm.
- For a single heavy app, open Settings > Apps, pick the app, then Storage and cache > Clear cache. Avoid Clear storage, which wipes the app's data and logins.
- Check Downloads for old installers, PDFs and videos you no longer need.
- On Samsung phones, Settings > Device care > Storage offers a similar clean-up.
Files by Google's help pages describe the Clean tab as the place for junk, duplicates, large files and unused apps, all handled on the device.
Why doesn't clearing junk free much space?
Caches are designed to come back. Clearing a streaming app's cache frees space today, and the app downloads it again tomorrow. Browsers and social apps can rebuild hundreds of megabytes within a week. That is not a fault: a warm cache is what makes a feed or a map load quickly on a slow connection.
Photos and videos, by contrast, do not regrow. On most phones they are the biggest single item in Settings > Storage, which is why removing duplicates and forwards recovers lasting space. The split between system junk and media is explained under storage cleaner vs gallery cleaner.
Do I need a junk cleaner app?
Usually not. Android's own settings and the free Files by Google app cover the safe options. Third-party junk cleaners add little beyond them, and some bundle speed or booster claims that Android does not need.
Where a dedicated app helps is with photos, which file-level tools cannot judge. GalleryJury, built for Android and coming to Google Play, leaves caches and installers to Files by Google and concentrates on clearing near-identical photos, junk screenshots and forwarded images, with deletions sent to the phone's trash first. For the whole job in order, see how to free up space on Android photos.
Frequently asked questions
Will clearing junk files delete my photos?
No. Caches, installers and temporary files are separate from your photos. Clearing an app's storage, rather than its cache, can delete downloaded content inside that app, so choose Clear cache.
How often should I clear junk files?
Only when storage is tight. Clearing caches constantly slows apps down, because they must rebuild data you will use again. Once a month or before a big download, such as a system update, is plenty.
Sources
- Files by Google Help: Free up space (checked 31 October 2026)
- Android Help: Free up space on your Android device (checked 31 October 2026)
Related
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GalleryJury is coming soon to Android
It keeps the best shot from every burst and clears the clutter around it. 50 free photos to try, then $5 for 5,000 photos or $15 for 20,000. Pay once, nothing renews. No subscription.