Free up Files storage

The iOS Files app is a window onto several locations. On My iPhone files live only on this device. iCloud Drive files live in iCloud (with local downloads). Downloads is usually Safari and app saves. Deleting from the wrong location can remove the only copy.

See how much space Files is using

Open the iPhone Settings app.
Tap General > iPhone Storage.
Look at iCloud Drive and large apps whose documents sit in Files.

Files itself is small. The documents are stored under On My iPhone, iCloud Drive, or another app location.

Clean On My iPhone

Open Files.
Tap Browse.
Under Locations, tap On My iPhone.
Open app folders and Downloads if it appears here.
Tap Select, pick large videos, ZIPs, and leftover exports, then tap the trash icon.

On My iPhone is local storage. There is no iCloud copy unless you also put the file in iCloud Drive. Deleting here can be permanent after Recently Deleted is emptied.

Clean Downloads

In Browse, open Downloads (under Locations or under On My iPhone, depending on iOS version).
Delete installers, duplicate PDFs, and videos you already saved elsewhere.

Safari, Mail, and other apps drop files here. These are user files, not cache.

iCloud Drive local downloads

In Browse, tap iCloud Drive.
Open a large file. If it was downloaded, you can remove the local copy by deleting it only if you mean to delete the iCloud file too.

Deleting in iCloud Drive deletes the cloud file for every device on that Apple ID, not just a cache. To keep the iCloud file and drop the local download, wait for iOS to evict unused downloads, or copy it elsewhere first if you are unsure.

Empty Recently Deleted

In Browse, tap Recently Deleted (Locations).
Tap Select, then delete items you do not need.

Recently Deleted still uses space. Emptying it is permanent.

Other locations

Third-party locations (Dropbox, OneDrive, Google Drive) in the Files sidebar are those apps. Deleting there follows that service. Use the matching guide if the large files sit in a connected cloud app.

Reinstall the app if storage is still high

If you already cleaned media and Files still looks huge, a fresh install can clear leftover cache and temp files that are hard to reach by hand.

Files is part of iOS. Do not delete it as an app reset. Copy anything in On My iPhone that is not also in iCloud Drive. iCloud Drive files stay if they finished uploading.
Delete the app from your phone.
Restart your phone.
Install Files again from the App Store or Google Play.
Sign in and restore from backup if the app offers it.

This often frees a lot of space. You may need to download some media again after restore.

What to do next

After Files is lighter, check your photo library for duplicates and similar shots. That is what Dedupo is for.

More app guides: Free up app storage.