📧 Email Image Guide
Compress Images for Email — Gmail, Outlook & Attachment Limits
Email image compression has a critical rule web images don't: WebP doesn't work in email. Gmail, Outlook, Apple Mail, and Yahoo Mail all show WebP as broken images. Use JPEG, use Target KB mode, and compress before you send.
WebP NOT supported in email clients
JPEG is the safe email format
Target KB mode for exact size control
Batch compress all photos at once
No upload — fully browser-based
0
email clients that support WebP (Gmail, Outlook, Apple Mail, Yahoo all reject it)
25 MB
Gmail total attachment limit per email
10 MB
typical corporate mail server limit (Outlook, Exchange)
300 KB
recommended maximum per inline email image
Compress Images for Email Free
Use Target KB mode for exact size control. JPEG output — safe for all email clients.
The Most Important Email Image Rule: No WebP
WebP is the best format for websites in 2025. It's also completely broken in email. Every major email client — Gmail (desktop and mobile), Outlook (Windows and Mac), Apple Mail (iPhone, iPad, Mac), Yahoo Mail, and virtually every corporate Exchange/Outlook environment — ignores WebP images and shows a broken image placeholder instead.
This isn't a browser support issue — email clients have deliberately restricted supported formats for security and rendering consistency reasons. There's no progressive enhancement or fallback mechanism for images in email the way there is in HTML with the <picture> element.
Never send WebP images in email. Use JPEG for photographs and PNG for images that require transparency or sharp edges. These are the only formats with universal email client support. GIF works for simple animation. WebP, AVIF, and HEIC all fail in email.
Email Client Format Support — Quick Reference
| Format | Gmail | Outlook | Apple Mail | Yahoo Mail | Verdict |
|---|
| JPEG | ✓ Supported | ✓ Supported | ✓ Supported | ✓ Supported | Safe — use for photos |
| PNG | ✓ Supported | ✓ Supported | ✓ Supported | ✓ Supported | Safe — use for logos/graphics |
| GIF | ✓ Supported | Partial (shows first frame only) | ✓ Supported | ✓ Supported | Use for simple animation only |
| WebP | ✗ Broken | ✗ Broken | ✗ Broken | ✗ Broken | Never use in email |
| HEIC | ✗ Broken | ✗ Broken | Partial | ✗ Broken | Never send HEIC via email |
| AVIF | ✗ Broken | ✗ Broken | ✗ Broken | ✗ Broken | Never use in email |
Email Size Limits — What You're Working Within
| Email Service / Server | Total Email Limit | Recommended Per-Image Target | Notes |
|---|
| Gmail | 25 MB total | <500 KB per image | Gmail shows "Large email" warning above 10 MB; recipients may have smaller limits |
| Outlook / Exchange (corporate) | 10–20 MB (admin-set) | <400 KB per image | Corporate servers often have stricter limits than Gmail; 10 MB is common |
| Yahoo Mail | 25 MB total | <500 KB per image | Same as Gmail limits; attachment count unlimited |
| Apple Mail | Server-dependent | <500 KB per image | Limit depends on the receiving mail server, not Apple Mail itself |
| HTML marketing emails (ESP) | No attachment limit | <200 KB per image | Images hosted via URL — size matters for load speed, not delivery limit |
Rule of thumb for attachment emails: If you're sending 10 photos, compress each to 400 KB target → total 4 MB, comfortably under any mail server limit. Use Target KB mode in the compressor and set it to 400 KB — the engine finds the highest quality that hits that target exactly.
How to Compress Images for Email — Step by Step
2
Drop your JPEG photos
Drop all the photos you want to send. HEIC from iPhone is automatically converted. No file count limit.
3
Switch to Target KB mode
Click the "Target KB" toggle in the settings bar. Set your target — 300–400 KB per image for attachments, 150–200 KB for inline email images.
4
Download as ZIP
Click "Download All" to get a ZIP of all compressed images. Extract the ZIP and attach the individual JPEG files to your email — not the ZIP itself.
Why attach individual files, not the ZIP? Many corporate email clients block ZIP files as a security measure (they can contain malware). Individual JPEG attachments pass through without issue. Gmail also allows recipients to preview individual image attachments inline — which doesn't work with a ZIP.
iPhone Photos (HEIC) — Converting for Email
iPhone photos taken in the default setting are saved as HEIC (High-Efficiency Image Container) — a format that's small and high-quality on the device, but widely incompatible when sent to non-Apple recipients.
When you AirDrop or email a photo from iPhone to another iPhone, HEIC works fine. When you email it to someone on Windows, Android, or a corporate email client, it may show as a broken attachment or a file they can't open.
The compressor at compress.html handles HEIC directly — drop your iPhone photos, and they're automatically decoded and re-encoded as JPEG. No manual conversion step. The result is a universally-compatible JPEG that any email client can display.
iPhone settings alternative: in Settings → Camera → Formats, switch from "High Efficiency" to "Most Compatible." This saves photos as JPEG directly. The tradeoff is larger files on-device — but JPEG compresses easily, and email compatibility is guaranteed.
Frequently Asked Questions
What image format should I use in email?
JPEG for photographs — universal support in Gmail, Outlook, Apple Mail, and Yahoo Mail. PNG for logos, screenshots, or images with transparency. GIF for simple animation (Outlook only shows the first frame). Never use WebP, HEIC, or AVIF in email — they display as broken images.
How do I compress images for email?
Open
convertlo.pro/compress.html, drop your JPEG photos, switch to Target KB mode, and set 300–400 KB as the target. The compressor runs up to 14 quality passes to hit the target exactly. Download everything as a ZIP and attach the individual files — not the ZIP — to your email.
Does WebP work in Gmail?
No. Gmail does not support WebP images — they display as broken image icons. This applies to Gmail in browsers, the Gmail mobile app (iOS and Android), and Gmail via desktop clients. Use JPEG for all email images.
What is the maximum email size for attachments?
Gmail: 25 MB total. Outlook/Exchange: 10–20 MB (admin-configured; 10 MB is most common in corporate environments). Yahoo: 25 MB. As a safe rule, keep total email size under 10 MB to reach all recipients — compress images to 300–400 KB each and you can send 20–25 photos comfortably.
How do I send multiple photos by email without it being too large?
Batch compress all photos to 300–400 KB each using Target KB mode in
the compressor. Download all as a ZIP, extract, and attach the individual JPEG files. Ten 400 KB photos = 4 MB total — well within any mail server limit. Don't attach the ZIP itself; attach the extracted JPEG files for better compatibility.
How do I resize photos for email on iPhone?
The easiest method: open
convertlo.pro/compress.html in Safari on your iPhone, tap the drop zone to browse your Photos library, drop your photos, set a Target KB (300 KB works for most email), and download the compressed JPEGs directly to your device. Then attach them from the Files app or your Downloads folder.