A full phone is not really about photographs most of the time. It is about WhatsApp, and about the copies of things you already have somewhere else.
Before you delete a single picture, look at where the space has actually gone.
Find out what is using the space
On most Android phones, open Settings, then Storage. You will get a list broken down by type: apps, images, videos, audio, documents, other. On an iPhone it is Settings, General, iPhone Storage, and it lists your apps largest first.
Nine times out of ten the biggest number on that screen is WhatsApp.
Clear the WhatsApp pile first
WhatsApp keeps every picture, video and voice note anyone has ever sent you, including the ones from groups you never read.
- Open WhatsApp and go to Settings, then Storage and data, then Manage storage.
- The top of that screen shows Larger than 5 MB. Open it, look through, and delete what you do not need. Videos here are usually the single biggest win.
- Below that, WhatsApp lists every chat by how much space it is using. Open the biggest ones and clear their media.
Deleting media from a chat does not delete the messages. The words stay; the pictures and videos go.
While you are in there, turn off automatic downloading so the pile does not build up again. Under Storage and data, set Media auto-download to No media for mobile data, and pick only photos for Wi-Fi.
Clear the app caches
A cache is the working scratch space an app keeps. Deleting it does not log you out or lose your data, and the app rebuilds what it needs.
On Android: Settings, Apps, pick the app, then Storage, then Clear cache. Do this for your browser, for Facebook and for anything else near the top of the list.
Clear cache is safe. Clear storage or Clear data on the same screen is not the same thing, and it will log you out and wipe that app's settings. Read the button before you tap it.
iPhones do not give you a cache button. Offloading an app does roughly the same job: Settings, General, iPhone Storage, tap the app, then Offload App. Your documents and data stay; the app itself is removed and comes back when you reinstall it.
Deal with downloads
Open your Files or My Files app and look in the Downloads folder. Most phones have years of things in there: every PDF anyone sent, installers, the same document downloaded four times. This folder is almost always safe to empty once you have checked nothing in it matters.
Then, and only then, the photographs
If you still need space, back the photos up before deleting anything. There is a whole guide on that: back up your photos and contacts.
A useful middle step is to shrink the ones you are keeping for paperwork rather than for memory. A scan of a certificate does not need to be 4MB.
What not to do
- Do not install a cleaner or booster app. They take space themselves, they show adverts, and everything they do you can do from Settings in five minutes.
- Do not delete folders you do not recognise inside Android or data. Those belong to your apps.
- Do not factory reset to free space. It deletes everything, and the phone will fill up again the same way.
Tools that help with this
Free, and they work inside your browser without uploading anything.