How to reduce image size on iPhone

Built-in options first, and what to reach for when you need an exact file-size number.

The short answer

iPhone's Photos app can crop a photo down, and Mail offers a rough size picker when attaching one. Both help, but neither lets you type an exact KB or pixel target and confirm it was met. If a form gives you a specific number, a compressor built around that requirement is the more direct route.

Option 1: Crop in the Photos app

Open the photo, tap Edit, then the crop tool. Cropping tighter reduces the pixel dimensions of what gets saved, which is the biggest lever for file size, and useful if your original is a full-resolution shot and the requirement you're working against is small, like an ID-style photo asking for a few hundred pixels wide.

Option 2: Mail's built-in size picker

When you attach a photo in the Mail app, a pop-up lets you choose between a few preset sizes (Small, Medium, Large, Actual Size) before sending. It does compress the photo, but you pick one of a handful of presets, not a specific KB or pixel number. That works when any smaller size will do, not when a form says "must be under 50KB."

Option 3: Check the format (HEIC vs. JPG)

With the camera set to High Efficiency, an iPhone saves photos as HEIC. HEIC files are smaller than JPGs of similar quality, which is good for storage, but plenty of upload forms only accept JPG or PNG.

When you pick a photo from your library in Safari and the site only accepts JPG, PNG, or WebP (as this site does), iOS usually hands over a JPG copy for you. If a form still rejects the file, go to Settings → Camera → Formats and choose Most Compatible. New photos are then saved as JPG. It doesn't change photos you've already taken.

Option 4: A browser-based compressor with an exact target

When a form gives you a number, like "under 100KB" or "600×600px," open IMAGE SIZE PRO's image compressor in Safari or any other iPhone browser. Type the limit, and it finds the highest quality that still meets it. You see a pass/fail check before you save, and you can choose JPG, PNG, or WebP as the output in the same step.

Common mistakes

Taking a screenshot instead of exporting. A screenshot captures your screen, not the actual photo file, and won't reliably hit a specific size or dimension target.
Assuming Mail's "Small" preset meets a stated KB limit. It reduces size, but by an amount the system chooses, so it isn't guaranteed to land under a specific number a form requires.
Not checking whether HEIC is accepted. If an upload silently fails or is rejected, format, not size, is a common overlooked cause.

Common questions

Why does my iPhone photo look huge compared to what a form accepts?

iPhone cameras capture at high resolution by default, so a single photo can run several megabytes, far above what most upload forms expect, which are often designed around files well under a megabyte.

Does switching to HEIC actually reduce file size?

Yes. HEIC stores a photo in less space than JPG at similar visual quality, and it's what the iPhone camera uses when set to High Efficiency. The catch is that some upload portals and older software only take JPG, so you may need a JPG anyway.

Can I hit an exact KB or pixel target using only the Photos app?

Not directly. The Photos app's crop and edit tools change dimensions, and Mail's send-size picker offers a few preset compression levels, but neither lets you type an exact number and get a pass/fail confirmation. For a specific requirement, a dedicated compressor is the more reliable path.