How to Compress a Photo on iPhone
The Preview app on iPhone can export a smaller JPEG with one slider. Apple's steps, how to check the new file size, and what to use when a form sets a hard limit.
To compress a photo on iPhone, open it in the Preview app, tap the button next to the file name, tap Export, choose JPEG, and drag the Size slider to the left. Preview is Apple's own app, so there is nothing to install, and the same steps compress any image on iPhone, screenshots included. If an upload form wants the file under a set size, such as 1MB, Compress Image takes a target in megabytes in Safari, and the photo is never uploaded.
The Preview, Photos, Camera and Mail steps below follow Apple's iPhone User Guide, which offered iOS 27 and iOS 26 editions when we read it on 25 October 2026.
Which iPhone route should you use?
| What you need | Use | What it changes |
|---|---|---|
| One smaller photo, no exact limit | Preview: Export as JPEG with the Size slider | Quality |
| A file under a set size for a form | Compress Image in Safari, with a target | Quality first, then width and height if needed |
| A JPG instead of HEIC | HEIC to JPG, or Photos' Most Compatible sharing option | Format |
| Smaller photos from now on | Camera settings: 12 MP instead of 24 MP | Pixels per photo |
How to compress a photo in Preview on iPhone
To compress a photo in Preview, export a copy with the Size slider moved left. These steps are from Apple's page Export or compress PDFs and images in Preview on iPhone:
- Open the Preview app and open the photo from Recents, Shared or Browse.
- Tap the button next to the file name, then tap Export.
- Choose JPEG as the format. HEIC has the same slider, but JPEG opens in more places once the photo leaves your Apple devices.
- Drag the Size slider. Apple's wording: left "for a smaller file size", right "for higher quality".
- Tap the done button, choose where to save the file, rename it in the Save As field if you like, and tap Save.
A new name makes the compressed copy easy to tell apart from the photo you started with. Apple describes the slider as a trade between file size and quality, and its page doesn't list width or height as an export option. Small steps to the left are hard to see on a phone screen. Large ones start to show as smudged fine detail and blocky patches in skies.
Check the new file size
Open the exported copy in Preview and tap the Info button. Apple's page Open and view PDFs and images in Preview on iPhone says it shows the file's size, along with its name and creation date. If the copy is still too big, export again from the original with the slider further left, rather than compressing the copy a second time. Each lossy save drops a little more detail, which lossy vs lossless compression explains.
The same Info panel shows the latitude and longitude a photo was taken at, when that information is in the file. Check it before you send a photo taken at home to someone you don't know.
If the slider alone can't get the file small enough, cut the pixels as well. Preview's Adjust Size does that, and how to resize a photo on iPhone walks through it.
How to compress a photo to a set size on iPhone
To compress a photo to a set size, open Compress Image in Safari and type the limit in megabytes. Preview makes you guess a slider position and check the result. The browser tool does the guessing for you.
- Open Compress Image and tap the drop area to choose one photo or up to 50. It is built for JPG, PNG and WebP files of up to 50MB each.
- To compress by quality, move the "Compression quality" slider. It runs from 0.3 to 1 and starts at 0.8.
- To hit a limit instead, type it into "Target max size in MB". The target takes priority over the slider.
- Tap Compress and download. Two or more photos come back together in one zip.
The tool counts 1MB as 1,048,576 bytes. If a form might count 1MB as 1,000,000 bytes, type a little under its limit, such as 0.95.
The target works in two stages. For a JPG, the tool first tries quality settings between 0.4 and 0.92 at full size. If even 0.4 overshoots, it shrinks the width and height, keeping the proportions, and tries again. A photo that is already under the target comes back unchanged, and at a quality setting the tool never hands back a file bigger than the one you gave it. Compressing an image to an exact size covers the process in more detail, and compressing an image to 100KB walks through one common small limit.
Everything happens inside the Safari tab on your phone. The photo is not sent to a server at any step.
What to do with a HEIC photo
Many iPhone photos are saved as HEIC, which our HEIC explainer covers, and plenty of websites and Windows programs won't open it. Compress Image is built for JPG, PNG and WebP, so give a HEIC photo to HEIC to JPG instead. It converts in the browser and has its own "JPG quality" slider, from 0.4 to 1, starting at 0.92. Lower it and the conversion compresses the photo as well.
From the Photos app, Apple's page Share photos and videos on iPhone gives a format choice when you share: tap the share button, tap Options, and pick Most Compatible, which Apple says means files "may convert to JPEG or MOV". That changes the format, not the quality, so pair it with Preview's slider or Compress Image if size is the problem.
How to make future iPhone photos smaller
On supported models, you can lower the resolution new photos are taken at. Apple's page Change advanced camera settings on iPhone gives the route: go to Settings > Camera > Formats > Photo Mode, then choose 12 MP or 24 MP. A 12 MP photo has half the pixels of a 24 MP one, so there is less to store. It only affects photos you take from then on. To change the format new photos are saved in, see how to stop your iPhone saving photos as HEIC.
Sending a large photo by email
Apple's sharing page says the attachment size limit "is determined by your service provider", not by the iPhone. Its page on adding email attachments in Mail says that when a file is over your account's limit, you follow the onscreen instructions to send it with Mail Drop. Apple's Mac Mail guide describes Mail Drop as uploading the attachment to iCloud. If you'd rather the photo stayed on your phone, compress it before attaching. Compressing a photo for email covers common limits and how small to aim, and on a computer, compressing an image on a Mac covers Preview, Photos and Mail there.
FAQ
Can I compress a photo without leaving the Photos app?
The sharing Options on Apple's page cover the file format, not a size or quality setting. For a smaller file, open the photo in Preview and use the Size slider, or use Compress Image in Safari.
Does compressing a photo on iPhone lower its quality?
Yes, a little. Moving Preview's Size slider left, or lowering Compress Image's quality, throws away detail to save bytes. At moderate settings it is hard to see on a photo; at the far left it shows. Always compress from the original, not from a copy you already compressed.
Can I compress several photos at once on iPhone?
Apple's Preview steps cover one open file. Compress Image takes up to 50 photos in one run and returns them in a single zip.
Are my photos uploaded anywhere?
Preview works on the iPhone itself, and Compress Image and HEIC to JPG run inside Safari, so the photos stay on your phone. Mail Drop is the exception, since it sends the attachment through iCloud.