For email, keep photos under 1MB each and under 5MB total for the attachment. JPEG is the right format for photographs. A smartphone photo is typically 4–12MB straight from the camera — compressing to under 1MB takes seconds and produces no visible difference on a screen.
| Email provider | Attachment size limit |
|---|---|
| Gmail | 25MB total message size |
| Outlook / Hotmail | 20MB total |
| Yahoo Mail | 25MB total |
| Apple Mail (iCloud) | 20MB (Mail Drop to 5GB) |
| Corporate / business email | Typically 10–20MB (varies by IT policy) |
The limit that actually causes bounced emails
Your provider's outbound limit is only half the equation. The other half is the recipient's inbound limit — and those are different numbers.
Gmail will send a 24MB attachment without complaint. But if the recipient's company runs its own mail server with a 10MB inbound cap, the email bounces after you send it. You get a delivery failure notification hours later, the recipient never saw it, and you have to start over.
Corporate mail servers are the common case here. A 10MB inbound limit is standard for many businesses. A 5MB total attachment size clears the vast majority of corporate configurations — which means keeping individual photos under 1MB when sending a handful of them together.
Why photographs should always be JPEG for email
A smartphone photo shot in standard JPEG mode is typically 4–8MB. The same photo in PNG format — which some export workflows produce — would be 15–30MB, because PNG stores every pixel losslessly and photographic data doesn't compress efficiently that way.
The quality difference between a JPEG at 85% quality and the original, viewed on a screen, is not visible to a human eye. The file size difference is 4–10x. For email, which is a screen-viewing context, JPEG is the correct format for every photograph.
PNG makes sense for screenshots, diagrams, charts, and images with text overlays — anything where sharp edges matter more than file size. More detail on the tradeoffs in our format comparison guide.
HEIC: the iPhone format most recipients can't open
iPhones shoot in HEIC by default since iOS 11. HEIC produces excellent image quality at half the file size of JPEG, which is why Apple uses it. The problem: Windows does not natively support HEIC, and neither do many Android devices or web-based email viewers.
When you attach a HEIC file from your Photos app on Mac or iPhone, some email clients convert it to JPEG automatically — and some don't. If there's any chance the recipient uses Windows, convert to JPEG before attaching. You cannot use our tool directly on HEIC files — export from your Photos app as JPEG first (File → Export → Export as JPEG on Mac), then compress.
What file size to target, by use case
The right target depends on what the recipient will do with the photo.
- Casual sharing (family, friends, social context): 200–500KB is plenty. Looks sharp on any screen, loads instantly, and takes up almost no mailbox space. Use compress to 200KB for fast casual sends.
- Business documentation (insurance claims, property listings, product shots): Under 1MB. High enough quality for close inspection, low enough to pass corporate filters.
- Sending to a printer or designer who needs to print it: Under 5MB. Beyond that, email is the wrong channel — use a file transfer service. A 5MB compressed file retains enough data for most print uses up to A4/Letter size at 300 DPI.
How to compress photos for email — step by step
- Check the format. If the file is HEIC, PNG, or any other format, export or convert to JPEG first. HEIC can be exported from iPhone Photos or Mac Photos app. PNG files can be converted by opening in any image viewer and saving as JPEG.
- Upload to our compressor. Drop the JPEG into resizeimageonline.net. Set the target to 500KB for casual sends, 1MB for business use.
- Download and attach. The compressed file downloads directly to your device — nothing is uploaded to a server. Attach to your email as normal.
- Check total attachment size before sending. Most email clients show the total size in the compose window. If you're sending multiple photos, confirm the combined size is under 5MB.
For batches of 10 or more photos, consider a cloud sharing link (Google Drive, Dropbox, iCloud) rather than compressing them all individually. Email is reliable for small sets; for large photo transfers, a sharing link is faster to send and easier for the recipient to download selectively.