The Complete Guide to Image Formats for Email
By ImgForge Team — Published February 13, 2026
Email is one of the most fragmented rendering environments on the web. Unlike a browser where you can rely on modern format support, email clients span decades of technology — from Outlook 2016 rendering on the Word engine to Apple Mail on the latest iOS. Choosing the wrong image format can mean broken images for a significant portion of your audience.
Why Image Format Choice Matters in Email
Email clients do not share a common rendering engine. Gmail, Apple Mail, Outlook, Yahoo Mail, and the dozens of other clients each handle HTML and images differently. A format that works perfectly in one client may display as a broken placeholder in another. Beyond compatibility, image file size directly affects load time, and large images can trigger spam filters or cause messages to be clipped by Gmail's 102 KB message limit.
JPG: The Safe Default for Photos
JPG (JPEG) is the most universally supported image format in email. Every major email client — including all versions of Outlook, Gmail, Apple Mail, Yahoo Mail, and mobile clients — renders JPG reliably. For photographic content such as product images, hero banners, and lifestyle photography, JPG is almost always the correct choice.
- Universal support across all major email clients including legacy Outlook versions
- Excellent compression for photographs, keeping file sizes manageable
- Lossy compression means quality degrades at low settings, and transparency is not supported
PNG: Best for Graphics, Logos, and Transparency
PNG is the second universally supported format in email and is the correct choice whenever you need transparency — for logos placed on coloured backgrounds, product cut-outs, or interface screenshots. PNG uses lossless compression, which means graphics with flat colours and sharp edges look crisp rather than blocky as they would in a compressed JPG.
- Full alpha channel transparency support, essential for logos on variable backgrounds
- Lossless compression keeps text, diagrams, and UI screenshots sharp
- Larger file sizes than JPG for photographic content — use JPG for photos, PNG for graphics
GIF: The Only Reliable Animation Format
GIF remains the only image format with animation support that works reliably across email clients. Animated GIFs are widely used in promotional emails for product demonstrations, countdown timers, and attention-grabbing banners. The main limitation is Outlook 2007–2019 on Windows, which only displays the first frame of an animated GIF rather than playing the animation.
- Animation support that works in Gmail, Apple Mail, Yahoo Mail, and most mobile clients
- Widely understood and supported format with no modern dependency requirements
- Outlook on Windows shows only the first frame — always design the first frame to be meaningful on its own
Why WebP and AVIF Do Not Work in Most Email Clients
WebP and AVIF offer superior compression compared to JPG and PNG, but their email client support remains too patchy to rely on. As of early 2026, Apple Mail and a handful of other clients support WebP, but Gmail, Outlook, and Yahoo Mail do not render it consistently. AVIF support is even more limited. Unlike browsers where you can serve WebP with a JPG fallback using the picture element, HTML email does not support a reliable fallback mechanism — a broken image is simply not rendered. Until all major clients support these formats, JPG and PNG remain the practical choice for email.
Image Size Limits and Email Performance
Large images slow down email rendering and can cause deliverability issues. Some general guidelines for keeping email images lean:
- Keep individual image files under 200 KB where possible. Hero images under 100 KB is an achievable target with modern compression.
- Keep the total email file size under 100 KB of HTML to avoid Gmail clipping the message. Images loaded from external URLs do not count toward this limit.
- Always host images on an external server and reference them by URL rather than embedding base64-encoded images inline — base64 dramatically inflates email size and is blocked by some clients.
Inline Images vs. Hosted Images
Email images can be either hosted externally (referenced by URL) or embedded as inline attachments using CID (Content-ID) references. Externally hosted images are the standard approach for marketing emails and newsletters. They keep email file sizes small, allow image tracking, and let you update the image after sending. Inline CID images are sometimes used in transactional or corporate email where images must display without internet access, but they increase attachment size and are often stripped by corporate email security gateways.
Retina and HiDPI Displays
A large proportion of email is read on high-resolution Retina displays — iPhones, iPads, and modern MacBooks all use displays with 2x or 3x pixel density. To ensure images look sharp on these devices, export images at twice the intended display size and set the width attribute in the HTML to the display size. For example, if an image will display at 600px wide, export it at 1200px wide and set width="600" in the img tag. This doubles the effective pixel density and eliminates the blurriness common on Retina screens.
Practical Tips for Email Newsletter Images
- Use JPG for all photographic content and PNG for logos, icons, and anything requiring transparency.
- Export images at 2x the display dimensions and constrain width in HTML for sharp rendering on Retina displays.
- Design animated GIFs so the first frame communicates the full message — Outlook users will only see it.
- Host all images on a reliable CDN or image hosting service and use absolute URLs, never relative paths.
- Always include descriptive alt text on every image — many recipients read email with images blocked by default, particularly in corporate environments.