How to compress an image for email (without losing quality)

A typical iPhone photo is somewhere around 4 to 6 megabytes. Send three of them in one email and you are bumping into the 25 MB Gmail limit. Send five and you are over. Outlook is even less forgiving — many enterprise inboxes cap attachments at 10 MB.

The fix is to compress the photos before attaching. Done right, this is invisible to the recipient: their eye cannot tell the difference between an 8 MB photo and a 600 KB version of the same photo. Done badly, you end up with a blurry, blocky mess.

The two things you can change

Image compression has two knobs. The first is quality. JPG and WebP both throw away some image data on save, and the quality slider controls how much. At quality 100 nothing is thrown away. At quality 50, a lot is. The interesting range is 70 to 90 — you save large amounts of file size with no visible difference.

The second is dimensions. Your phone shoots at 4000 by 3000 pixels. Your colleague is going to look at it on a 1920 by 1080 monitor or a phone screen. Resizing the image to 1600 pixels wide before saving cuts the file size dramatically and the difference is invisible at the size they will view it.

The recipe that works

For a photo you are emailing to someone who will look at it on a screen:

Resize to 1600 px on the long edge
Save as JPG at quality 80

That gets you from a 6 MB photo to roughly 400-700 KB without any visible quality loss. Five photos fit comfortably in any inbox.

For a photo you are emailing for printing or archival use, skip the resize and save at quality 90 instead. The file will be larger but the photo will be sharp at print sizes.

Doing it without uploading anywhere

A lot of online compressors ask you to upload your photos to their servers. That works, but your photo passes through someone else's machine first. For a holiday snap that is fine. For a passport photo, an ID card, or a screenshot of a private chat, it is less fine.

Modern browsers can do this work locally. Our image compressor drops your photo into a Web Worker, runs the compression in JavaScript, and gives it back. Your photo never leaves the browser tab. You can verify this — open your developer tools, go to the Network tab, and process a photo. Nothing gets uploaded.

Common mistakes

Saving a JPG over and over loses quality each time. If you compressed at quality 80, then opened the file and saved it again at quality 80, you are now at "quality 80 of quality 80" — which is more like quality 65. Always compress from the original photo, not from a previously compressed copy.

Saving a PNG with a quality slider does nothing. PNG is lossless — the slider is ignored. If you need a smaller PNG, what you actually want is a different format. JPG for photos, WebP for general use, PNG only for screenshots and graphics that need transparency.

Cropping does not compress. Cutting a photo down to the interesting part removes pixels, so the file is smaller, but it is a different photo. Compression keeps the same image and shrinks the data behind it.

What about WebP?

WebP is roughly 25 to 35 percent smaller than JPG at the same visible quality. Every modern email client can show WebP, but a few corporate firewalls still strip them out, and old Windows photo viewers cannot open them. For email to a stranger, JPG is still the safe choice. For a personal site or a chat with a tech-friendly friend, WebP wins.

Try it

If you have a photo open in Photos right now, save it to your desktop, drop it into the Fileoholic image compressor, and try quality 80 with a 1600 px max dimension. Compare the file size to the original. That is your new email-ready version.