Definition
Browser rendering describes how a web browser interprets and displays the HTML and CSS of an email viewed through a web-based email client. Unlike desktop or mobile email apps, browser-rendered emails are subject to the rendering engine of the specific browser (Blink for Chrome, WebKit for Safari, Gecko for Firefox) combined with the email client's own CSS transformations.
This creates a complex rendering environment where an email may look different depending on the browser, the email client, and their interaction.
Rendering Engines and Email Clients
| Browser | Rendering Engine | Affected Email Clients |
|---|---|---|
| Chrome | Blink | Gmail (Chrome), Yahoo Mail (Chrome) |
| Safari | WebKit | Apple iCloud Mail, Gmail (Safari) |
| Firefox | Gecko | Gmail (Firefox), Yahoo Mail (Firefox) |
| Edge | Blink (Chromium) | Outlook.com, Office 365 (browser) |
Common Browser Rendering Differences
- CSS support: Chrome supports more modern CSS than Firefox in email contexts
- Font rendering: Different browsers render web fonts and system fonts differently
- Image handling: Each browser has different default image loading behaviours
- Interactive elements: AMP for Email and hover effects vary by browser support
- Dark mode: Each browser/email client combination handles dark mode colour inversion differently
- Responsive design: Media query support and behaviour varies across browsers
Testing Browser Rendering
- Test across browsers: Preview emails in Chrome, Safari, Firefox, and Edge
- Use rendering tools: Litmus and Email on Acid simulate browser rendering
- Check browser-specific quirks: Some browsers have known issues with specific CSS properties
- Test on different OS: Rendering differs between macOS and Windows for the same browser
Related Glossary Terms
Dark Mode
Dark mode in email refers to how email clients render messages when the recipient has dark mode enabled. It affects colour display, image rendering, and readability. Designers use CSS media queries and hybrid coding techniques to control the dark mode appearance.
Drag-and-Drop Email Editor
A drag-and-drop email editor is a visual interface that allows marketers to build email layouts by dragging content blocks into place without writing HTML or CSS code.
Email Accessibility Guidelines
Email accessibility guidelines ensure emails are usable by people with disabilities, following WCAG standards for screen readers, colour contrast, keyboard navigation, and readable content.
Email Accessibility
Email accessibility ensures marketing emails are usable by people with disabilities, including those using screen readers, keyboard navigation, or assistive technologies. It follows WCAG 2.1 guidelines for structure, contrast, semantics, and descriptive content.
Email Body
The email body is the main content area of an email message, containing the visible text, images, and structural elements that communicate the message to the recipient.
Email Brand Guidelines
Email brand guidelines document the specific rules for logo usage, colour palette, typography, tone of voice, and component specifications across all email communications.
Frequently Asked Questions
Chrome (Blink) generally offers the broadest CSS support and most predictable rendering. Safari (WebKit) has stronger standards compliance but more limitations. Firefox offers good standards support but has a smaller email client user base.
Yes. Web-based email (Gmail, Yahoo, Outlook.com) accounts for approximately 60-70% of email opens, making browser rendering the most important consideration for email design. Mobile apps and desktop clients make up the remainder.
Optimise for the browsers your audience uses by checking your analytics for browser-level open data. If unavailable, prioritise Chrome (most popular) and Safari (significant market share among mobile and Mac users).