How to compress images for email on a Mac

Attach a handful of photos and your email bounces, or takes ages to send. Email providers cap how big a message can be, and full-size images hit that limit fast. Here's how to shrink them so they go through — and arrive quickly on the other end.

How big can an email be?

Limits checked October 2026. Work and school accounts may have different limits.

One catch: attachments grow by roughly a third when they're sent, because of how email encodes files. So 18 MB of photos can be too big for a 20 MB limit. Aim to stay well under — 10–15 MB total is a safe target.

1. Use Apple Mail's Image Size menu

When you attach photos in Apple Mail, an Image Size menu appears on the right side of the message header. Choose Small, Medium or Large instead of Actual Size, and Mail shrinks the photos before sending. Quick and built in, but it only works in Mail and the result can be blurry if you go too small.

2. Send the originals with Mail Drop

If the recipient needs full-quality files, Apple Mail can send big attachments with Mail Drop: the files are uploaded to iCloud and the recipient gets a download link that expires after 30 days. Good for originals — but it's a link, not an attachment.

3. Compress the images before attaching

For attachments that are small but still look great, compress them first. Drag the images into TinyPresso, choose JPEG as the output format, and press Compress. In our test a 2.4 MB landscape image came out at 392 KB as a JPEG — so ten images like it drop from about 24 MB, too big for most email, to under 4 MB.

Then attach the compressed copies from your export folder. Everything happens on your Mac, so private photos aren't uploaded anywhere.

Tips for email-friendly images

• Send photos as JPEG. It opens on every phone, PC and email app. HEIC and WebP save more space but some recipients can't open them.
• Keep screenshots as PNG. Text stays sharp — just compress them first. Our Retina screenshot went from 875 KB to 261 KB.
• Many photos? Use a link. For dozens of full-size photos, a shared album or cloud link is kinder to everyone's inbox.

Related guides

• How to compress JPEG files on a Mac
• HEIC vs JPEG: which photo format should you use?
• How to reduce image file size on a Mac

FAQ

What is the maximum attachment size for email?

Gmail allows 25 MB per message, while iCloud Mail and Outlook.com allow about 20 MB. Because attachments grow by roughly a third when sent, it's safest to keep attachments to 10 to 15 MB in total.

How do I make a photo smaller to email from my Mac?

In Apple Mail, use the Image Size menu and choose Small, Medium or Large. To control quality yourself, compress the photos first with TinyPresso, choosing JPEG as the output format, then attach the smaller copies.

Which image format is best for email?

JPEG for photos, because every device and email app can open it. Use PNG for screenshots so text stays sharp, and compress both before attaching.