How to free up storage on iPhone: what to delete and what to check first

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"Storage Almost Full" usually appears at the worst moment, when you are trying to take a photo or install an update. Before you start deleting things at random, find out what is actually using the space. Menu names below are from recent versions of iOS; if one does not match your phone, search for the setting in the Settings app.

Step 1: check what is using space

Go to Settings > General > iPhone Storage. After a moment it shows a coloured bar by category and a list of apps sorted by size. It also offers recommendations, such as reviewing large attachments or turning on offloading, which you can apply with a tap. Tap any app to see how much is the app itself and how much is its Documents & Data. A messaging or streaming app with a few gigabytes of data is often the real culprit.

Offload apps you rarely use

Offloading removes the app but keeps its documents and data. The icon stays on your Home Screen with a small cloud; tap it and the app downloads again with everything as you left it.

To offload one app: Settings > General > iPhone Storage, tap the app, then Offload App.
To do it automatically, turn on Offload Unused Apps (offered in iPhone Storage and in the App Store settings).

Offloaded apps need an internet connection to reinstall, and an app removed from the App Store cannot be downloaded again, so think before offloading something you rely on. Delete App removes everything, data included.

Photos and videos

Photos and videos are usually the biggest category.

With iCloud Photos on, choose Optimise iPhone Storage in the Photos settings. Full-resolution originals stay in iCloud and the phone keeps smaller versions. You need enough iCloud storage for your whole library.
Empty Recently Deleted in the Photos app. Deleted photos stay there for about 30 days and still take up space.
Look for duplicates (Photos can find and merge them in the Utilities section) and long videos you no longer need.
Recording video in 4K at high frame rates uses much more space; lower it in the Camera settings if you do not need it.

Messages

Years of photos, videos and voice notes in chats add up.

In the Messages settings, set Keep Messages to 30 days or 1 year instead of Forever. This deletes older messages and their attachments, so back up anything important first.
In iPhone Storage > Messages, review large attachments and delete them by type.
Check other chat apps too: many have their own storage-management screen.

Safari and other caches

In the Safari settings, Clear History and Website Data removes cached files. This also signs you out of websites. Other apps, especially streaming and social apps, keep large caches; downloaded films, podcasts and music offline are often forgotten.

What is "System Data"?

System Data is the grey part of the bar: caches, logs, temporary files and other things iOS manages itself. You cannot delete it directly, and it can grow quite large. It often shrinks after clearing caches in individual apps, deleting old message attachments, or simply restarting the phone. Installing the latest iOS update also tends to tidy it.

When to back up and reset

If System Data stays huge and nothing else helps, a clean start can recover a lot of space:

Make a full backup to iCloud or to a computer.
Check the backup has completed.
Use Transfer or Reset iPhone > Erase All Content and Settings in General.
Restore from your backup.

This is a last resort and takes time, so try everything above first.

Keep it under control

Check iPhone Storage every few months.
Turn on offloading if you install and forget apps.
Consider more iCloud storage if your photo library keeps growing.

Share what freed the most space on your phone, or ask about a stubborn storage problem, in the comments.