How to reduce photo file size on iPhone

A normal iPhone photo is a couple of megabytes. A thousand of them will not fill a modern phone the way a handful of long videos will. If your library feels heavy and you assume photos are the reason, it is worth checking that assumption before you start compressing everything in sight.

The photos actually worth finding

A small number of file types weigh far more than an ordinary snapshot, and they are the ones worth hunting down specifically rather than treating your whole library as suspect.

• ProRAW and RAW. Roughly 25 to 75 MB each, because they store far more sensor data than a compressed JPEG or HEIC. Only shows up if you shoot in ProRAW mode on a supported iPhone — most people never turn it on, but if you did once and forgot, this is usually where the surprise is.
• Panoramas. Stitched from many frames into one very wide image, so the pixel count, and the file size with it, is much higher than a standard photo.
• Imported camera files. Anything brought in from a real camera — a DSLR, a mirrorless body, a drone — is usually a different weight class from anything your iPhone's own camera produces.
• Full-page screenshots. A scrolling capture of an entire webpage or document is dramatically heavier than an ordinary screenshot, because it is stitching several screens' worth of content into one tall image. Ordinary screenshots are usually small enough that clearing them out is about tidiness, not storage.

Settings → Camera → Formats: HEIF or JPEG

This toggle has been set to High Efficiency by default since the iPhone 7, and it saves photos as HEIC, which Apple describes as compressing better than an equivalent JPEG at the same visual quality. Most Compatible saves JPEG instead — larger files, but ones that older software and some third-party services still expect without converting them first.

Two things worth knowing about it. First, it changes new photos only — switching from Most Compatible to High Efficiency does not shrink anything already in your library. Second, sharing an HEIC photo to an app or service that does not support the format converts it to JPEG automatically for that share, which is why file sizes sometimes look inconsistent between what is on your phone and what ends up elsewhere — the stored original did not change, a converted copy was made for the trip.

Resizing and compressing are not the same operation

Compressing keeps a photo's dimensions the same and reduces the file size by encoding it less generously — the picture is still, say, 4032 by 3024 pixels, just stored more efficiently. Resizing actually shrinks those dimensions, to something like 2000 by 1500, which also reduces file size but permanently reduces how much detail is there if you later want to crop tightly or print large.

Which one is right depends on what you are keeping the photo for. A photo you will only ever view on a phone screen loses nothing meaningful from resizing. One you might print, or crop hard into later, is better served by compression, which trims the file without touching the pixel count. Slean does both — resize under the photo tools, compress with a size preview — so the choice is explicit rather than accidental.

Finding the heavy ones is a size sort

Photos has no size column for images, no size sort, and no size filter — the same gap it has for video. The direct route is the same fix: sort the library largest file first. Set the filter to photos, order by size, and the ProRAW files, panoramas and long screenshots rise to the top in seconds instead of turning up by accident months later. The full case for size sorting, including why length and file type are not reliable proxies, is here.

Android has the same shape of problem with a different set of menus. How storage triage works there.