How to Reduce Image File Size on Windows, Mac, iPhone and Android

Resizing gives the biggest savings. Halving the width and height leaves a quarter of the pixels, and the file shrinks roughly in proportion. Lowering the JPG quality comes next, and it keeps the dimensions as they are. Converting a photo from PNG to JPG can make it several times smaller. Removing metadata saves the least, but it also strips details like your GPS location.

Built-in tools are fine when any smaller file will do. If a form or website gives you a hard limit in KB, you end up resizing and re-saving by trial and error, and that's where a tool with a target size saves time.

Windows 11 has two built-in options. The Photos app is the more useful one because it can lower the JPG quality as well as the dimensions. Paint only changes the dimensions, but it's on every version of Windows and can turn a PNG or BMP file into a JPG.

To shrink a photo with the Photos app:

1. Right-click the image and choose Open with → Photos.
2. Click See more (the three dots at the top of the window) and choose Resize image.
3. Choose Pixels, keep Maintain aspect ratio on, and enter a smaller width or height. 1920 px on the longest side is plenty for screens; 1280 px is enough for most web forms and profile photos.
4. If the image is a JPG, drag the Quality slider down to around 80.
5. Click Save, give the file a new name so the original stays untouched, and save it.

Preview, the app that opens images by default, can resize a picture and re-save it as a JPG at any quality. When you export, it shows the resulting file size under the quality slider, so you can adjust until the number is right.

Preview edits the open file directly. To keep the original, select it in Finder, press Command-D to make a copy, and open the copy instead.

1. Open the image in Preview and choose Tools → Adjust Size.
2. Check Scale proportionally and Resample image, then enter a smaller width or choose a preset from the Fit into menu. Click OK.
3. Choose File → Export and set Format to JPEG.
4. Drag the Quality slider toward Least and watch the File Size estimate below it. Somewhere around the middle is usually a good balance.
5. Click Save.

The Photos app has no compress button, but iOS still gives you a few ways to end up with smaller files, depending on what you need them for.

For email: when you attach photos in the Mail app, you can send them at Small, Medium, Large or Actual Size. Depending on your iOS version, the choice appears when you tap Send or in the Cc/Bcc, From area of the message. Large is a good default for photos people will view on a screen.

HEIC or JPG: iPhones normally save photos as HEIC (High Efficiency under Settings → Camera → Formats), which takes noticeably less space than JPG. Switching to Most Compatible makes every new photo a JPG that any website accepts, but the files get bigger. If you only need JPGs when you copy photos to a computer, leave the camera setting alone and set Transfer to Mac or PC to Automatic in the Photos settings (Settings → Apps → Photos on iOS 18 and later).

For photos you resize often: the Shortcuts app can resize and re-save photos in one tap. You only have to build the shortcut once:

1. Open Shortcuts and tap + to create a new shortcut.
2. Add the Select Photos action. Turn on Select Multiple if you want to process several photos at once.
3. Add Resize Image and set the width, for example 1600. Leave the height on Auto Height so the proportions stay the same.
4. Add Convert Image, set it to JPEG, lower the Quality a little and turn off Preserve Metadata.
5. Add Save to Photo Album, give the shortcut a name and run it.

Android phones vary more than iPhones because each manufacturer ships its own gallery and camera apps, so menu names depend on the brand and Android version. These are the options you're most likely to have.

Samsung Galaxy: open the photo in Gallery, tap the edit (pencil) icon, then More options (⋮) → Resize. Pick a percentage, tap Done, then save. To keep the original, tap More options → Save copy instead of Save. Photos can only be made smaller, not larger.

Google Photos: there's no resize option, but cropping removes pixels and makes the file smaller. Tap Edit → Crop, then save the result as a copy. The Storage saver backup setting only compresses the copies in your Google account, not the photos on your phone.

Camera settings: if every photo is much bigger than you need, lower the resolution in your camera app. Look for a setting called picture size, resolution or megapixels. It only affects new photos.

For an exact size in KB: open FormShrink in Chrome on your phone. It works the same way as on a computer, and your photos stay on the device.

Built-in tools leave you guessing: resize, save, check the size, try again. FormShrink lets you enter the size you need and does the trial and error for you. It runs in your browser with WebAssembly, so your images are never uploaded, and it's free with no sign-up.

For common limits, start from a preset page: 20KB, 50KB, 100KB, 200KB or 1MB. Each one opens the tool with JPG output, the target size and a sensible resize limit already filled in. For anything else, use the image compressor:

1. Drag up to 10 images onto the page or click Browse Files. JPG, PNG, WebP, GIF, BMP and TIFF all work, up to 50MB each.
2. Stay in Smart mode to let FormShrink pick the format and quality with a single slider, or switch to Advanced mode to set the Output Format, quality, Resize Image and a target size in KB.
3. Click Compress Images, compare the original and compressed sizes, then Download each file or click Download All.

Sometimes the pixel size is fixed: a portal wants exactly 600 × 600, or you need full resolution for printing. You can still shrink the file by changing how those pixels are stored.

Lower the JPG quality. Phone cameras save JPGs at a high quality setting. Re-saving at around 75–85 often cuts the size roughly in half, with no difference you'd notice at normal viewing size. In Preview, skip Adjust Size and just use the Quality slider in File → Export.

Save photos as JPG, not PNG. PNG is lossless, which is right for screenshots and logos but wasteful for photos. A photo saved as PNG can easily be several times larger than the same photo as a JPG.

Drop the metadata. Camera details, GPS location and embedded previews usually add somewhere between a few KB and a few dozen KB. That matters mainly for small targets, and removing your location is good for privacy anyway. FormShrink doesn't carry camera metadata over to the compressed file.

Use a more efficient format if the site accepts it. HEIC and lossy WebP hold the same quality in fewer bytes than JPG, but many upload forms still take only JPG or PNG, so check before you convert.

To keep the exact dimensions in FormShrink:

1. Open the image compressor and switch to Advanced mode.
2. Set Output Format to JPEG and make sure Resize Image is off.
3. Enter your limit under Target size (KB, optional) and click Compress Images. The result has the same width and height as the original.

Gmail allows 25MB of attachments per message and Outlook.com 20MB; bigger files get turned into a Google Drive or OneDrive link instead. Attachments also grow by about a third when they're encoded for sending, and the recipient's mail server may have a lower limit of its own, so aim well below the headline number.

For photos people will look at on a screen, 1600 to 2048 pixels on the longest side is plenty, and a JPG of that size is typically 200–500KB. Ten photos then add up to a few megabytes instead of 30MB or more.

Your mail app may resize photos for you. Mail on iPhone offers Small, Medium, Large and Actual Size; Mail on the Mac has an Image Size menu in the message window; and classic Outlook for Windows has Resize large images when I send this message under File → Info, which scales pictures down to about 1024 × 768.

For more control, compress the photos before you attach them. Compress to 200KB fits each photo within 1920 px, enough to fill a laptop screen, and compress to 500KB keeps up to 2560 px for recipients who may want to zoom in.