Imagery treatment for email marketing: formats, sizes & best practices
Joey Lee
September 4, 2025
Images can make or break your email marketing. Done right, they draw attention, guide the eye, and elevate your brand. Done wrong, they slow load times, distort layouts, or trigger spam filters.
In this guide, we’ll cover everything you need to know about email imagery: ideal file formats, recommended sizes, optimization techniques, and responsive best practices. Whether you’re designing hero banners or product grids, this article will help you build beautiful, effective, and high-performing emails.
Why optimizing images matters
Better deliverability: Large or bloated image files can flag spam filters or prevent messages from loading entirely.
Faster load times: Emails that load in under 2 seconds get higher engagement rates.
Cross-device consistency: Optimized images scale properly across mobile, tablet, and desktop.
Improved accessibility: Proper alt text ensures that all users, including those with visual impairments, understand your message.
💡 43% of email opens happen on mobile, so optimizing image size and responsiveness is no longer optional.
Email image dimensions: what’s the ideal size?
Use case | Recommended width | Notes |
Full-width banner / hero | 600–900 px | Most email clients display content up to ~650 px wide |
In-body / product images | 300–600 px | Adjust to fit columns or modules |
Logos/icons | 50–100 px | Use PNG for crisp visuals and transparency |
2-column layout | 280–300 px | Each column should be under 50% of total width |
3-column layout | 180–200 px | Consider text wrapping or icon spacing |
✅ Height can be flexible, but keep the most important visuals within the first 300–500 px (“above the fold”).
Recommended file formats for email
Format | Best for | Pros | Cautions |
JPEG | Photos, backgrounds | Small file size, wide support | No transparency support |
PNG | Logos, icons, UI elements | Crisp lines, supports alpha | Larger file sizes |
GIF | Simple animations | Attention-grabbing motion | Large files, limited colors |
WebP | Photos + transparency | Small and flexible | Not supported in all clients |
SVG | Scalable icons and graphics | Resolution independent | Limited support in Gmail and Outlook |
🚫 Avoid embedding text inside images unless necessary. Many users have image-blocking enabled, and you risk losing key messaging.
Best practices for file size
Stay under 100 KB per image whenever possible.
Total email size (including HTML, text, and images) should ideally stay below 1 MB.
Use tools like TinyPNG, ImageOptim, or Squoosh to compress assets without losing quality.
Responsive image design for email
Modern email audiences are mostly mobile, so image responsiveness is key. Here’s how to ensure your visuals look great on every screen:
✅ Consider retina optimization
Export high-resolution images at 2x size (for example, 1200 px wide for a 600 px display area) to look sharp on retina screens.
✅ Use alt text for accessibility
This helps screen readers describe the image and ensures fallback messaging if the image doesn’t load.
Balance text and image
Spam filters are more likely to flag emails that are overly reliant on images. Try to maintain a 60% text / 40% image ratio.
🟡 Image-only emails are also a poor experience for users with image loading turned off.
Workflow tips for designers and marketers
Plan image purpose: Decide whether it’s decorative, informative, or actionable.
Pick the right format: JPEG for photos, PNG for logos and UI, GIF for light animations.
Export at correct dimensions: Resize for target layout and device.
Compress efficiently: Use tools to reduce file size without losing quality.
Apply responsive HTML and CSS: Make sure images scale across devices.
Write clear alt text: Always describe the content or purpose of the image.
Test across clients: Check Gmail, Outlook, Apple Mail, and mobile apps for consistency.
Summary: email image optimization cheatsheet
Aspect | Best practice |
Width | 600–650 px standard |
File size | ≤ 100 KB per image |
Format | JPEG (photos), PNG (icons), GIF (lite) |
Responsive HTML | width: 100%, max-width: 600px |
Alt text | Short, clear, descriptive |
Retina display support | Export images at 2x resolution |
Text/image ratio | At least 60% text to 40% image |
Final thoughts
Great visuals can elevate your email campaigns, but only if they’re optimized for performance, accessibility, and responsiveness. By following the image sizing and formatting rules above, you’ll avoid common pitfalls and ensure your content is as sharp and strategic as your subject lines.
Want help implementing these best practices into your email design system or templates? Let’s talk.
