Glossary · Thumbnail cache
What is a thumbnail cache? The .thumbnails folder on Android
Short answer
A thumbnail cache is a store of small preview images that a gallery or file manager creates so it can show your photo grid quickly. On Android it lives in hidden folders such as DCIM/.thumbnails or inside each app's own cache. Clearing it is safe and frees some space, but the previews are rebuilt the next time you browse.
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Why do galleries keep thumbnails?
Decoding a full 12 MP photo for every tile in a grid would make scrolling slow and drain the battery. Instead, a gallery decodes each photo once, saves a tiny version and reuses it. The system MediaStore can also generate thumbnails for apps that ask, and Google Photos keeps its own previews of photos stored only in the cloud so they appear instantly.
The folder name starts with a dot, which hides it from most galleries. A file manager with "show hidden files" turned on reveals it.
Thumbnails are generated at a few fixed sizes. A grid tile might use a preview of 256 or 512 pixels on the long side, while a full-screen preview needs a larger one, so a single photo can have several cached versions.
How big can a thumbnail cache get?
Each preview is small, often tens of kilobytes, but they add up with a large library. Older Android versions kept a single large file in DCIM/.thumbnails that could grow past a gigabyte. Modern phones split previews by app, and apps prune them over time, so caches tend to stay in the low hundreds of megabytes.
| Where | What is inside | Safe to clear? |
|---|---|---|
| DCIM/.thumbnails | Legacy previews from the system or older galleries | Yes |
| Gallery app cache (Settings > Apps) | Grid previews and edits in progress | Yes, via Clear cache |
| Google Photos cache | Previews of cloud and local photos | Yes, via Clear cache |
Some cleaner apps report the thumbnail cache as junk and promise large savings from deleting it. The gain is real but temporary, and the gallery spends battery rebuilding what was removed.
Previews can also outlive their photos. When a file is deleted outside the gallery, its thumbnail may linger until the cache is cleared, which is one reason ghost tiles appear.
How do you clear it safely?
- Open Settings > Apps, choose your gallery app, then Storage.
- Tap Clear cache. Do not tap Clear storage or Clear data unless you mean to reset the app.
- Optionally, in a file manager, delete the contents of DCIM/.thumbnails.
- Open the gallery and let it rebuild the previews.
The space comes back only until the next browse, so this is a fix for glitches rather than a lasting saving. For that, deleting photos you do not need works better; start with phone storage full: what to do. The wider topic of cached data is on the app cache page.
Clearing Google Photos' cache is fine too; cloud previews download again over Wi-Fi.
Frequently asked questions
Will deleting .thumbnails delete my photos?
No. The folder holds only previews. Your original images in DCIM/Camera and other folders are untouched.
Why does the .thumbnails folder come back?
Galleries recreate it whenever they need previews. You can delete it again, but the gallery will rebuild it as you scroll.
Sources
- Android Help: Free up space on your Android device (checked 31 October 2026)
- Android Developers: Access media files from shared storage (checked 31 October 2026)
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