1. See what's taking up space
Go to Settings → General → iPhone Storage. At the top there's a bar split by category (apps, photos, iOS, system data…) and below it your apps sorted by size. It takes a few seconds to calculate.
On that same screen, iOS shows recommendations based on how you use your iPhone, such as offloading apps you don't use or reviewing large Messages attachments. Tap Show All to see them. They vary from iPhone to iPhone, so you may not see all of them.
2. Photos and videos: where the space usually is
On most iPhones, the photo library is the biggest item. In order of speed:
- Empty Recently Deleted. What you delete keeps using space for 30 days. Go to Photos → Collections → Recently Deleted, tap View Album, then ••• and Delete All. It's the quickest space you'll get back.
- Review your videos. One minute of 4K video takes hundreds of MB. Collections → Media Types → Videos has them all in one place.
- Clear screenshots and screen recordings. They pile up without you noticing. See how to delete all your screenshots.
- Merge duplicates in Collections → Utilities → Duplicates. More in duplicate photos on iPhone.
- If you use iCloud Photos, turn on Optimize iPhone Storage in Settings → [your name] → iCloud → Photos. Your iPhone keeps lightweight versions and the originals stay in iCloud.
3. Messages and WhatsApp
- Messages: in Settings → Apps → Messages → Keep Messages, change Forever to 1 Year or 30 Days. iOS deletes older conversations, attachments included. In iPhone Storage → Messages you can also review the largest attachments.
- WhatsApp: it has its own manager in its settings, under Storage and Data → Manage Storage, with the largest files and the chats that take up the most space. If saving to Photos is on, everything people send you also ends up in your photo library.
4. Apps you no longer use
In the iPhone Storage list, tap an app to see how much space the app and its data take. You have two options:
- Offload App: removes the app but keeps its documents and data. Reinstall it and everything comes back.
- Delete App: removes the app and its data.
To have iOS do this automatically for apps you don't open, turn on Offload Unused Apps in Settings → Apps → App Store. Also check downloads in TV, movie, music and podcast apps: they're often several forgotten GB.
5. “System Data”: what it is and what you can do
It's a category iOS manages on its own: Siri voices, fonts, dictionaries, caches, logs and search indexes. It grows and shrinks by itself, and iOS clears caches and temporary files when it needs room. You can't delete it by hand.
Quick checklist
- Empty Recently Deleted in Photos.
- Delete videos you don't need and old screenshots.
- Merge Duplicates.
- Set Keep Messages to 1 Year.
- Clean up WhatsApp from its own storage manager.
- Offload the apps you don't use.
FAQ
Why is “System Data” so big?
Because it includes caches, logs and resources iOS downloads and manages on its own. It usually shrinks after a while or after an iOS update. There's no safe way to delete it by hand, and no app can do it for you.
If I buy more iCloud storage, will my iPhone have more space?
Only if you use iCloud Photos with Optimize iPhone Storage on: then your iPhone keeps lightweight versions and the originals live in iCloud. More iCloud storage on its own doesn't remove anything from your iPhone.
What happens if storage fills up completely?
You can't take new photos, iOS updates won't install and some apps misbehave. It's worth always keeping a few GB free.