Why Does Email HTML Look Different?
Understanding email rendering differences and client compatibility
Table of Contents
Why Does Email HTML Look Different?
Email HTML looks different in browsers and email clients due to fundamental differences in how email clients render HTML compared to web browsers. Email clients have limited HTML and CSS support, use different rendering engines, and may modify HTML for security reasons.
Email HTML must be designed specifically for email clients, not web browsers, to ensure consistent rendering. What works perfectly in a web browser may not work or may look completely different in email clients.
Extract and analyze email HTML using our extract email HTML tool, and validate HTML code with our HTML validator to ensure email client compatibility.
Rendering Differences
1. Different Rendering Engines
Email clients use different rendering engines than web browsers. Gmail, Outlook, Apple Mail, and other clients each have their own rendering engines with different capabilities and behaviors.
2. Limited HTML Support
Email clients support only a subset of HTML features. Many HTML elements and attributes that work in browsers are not supported or behave differently in email clients.
3. Security Restrictions
Email clients restrict certain HTML/CSS features for security reasons, preventing JavaScript, external resources, and potentially dangerous code from executing.
4. Table-Based Layouts
Email clients rely heavily on table-based layouts. Modern CSS layout methods (flexbox, grid) may not work, requiring traditional table structures.
5. Inline Styles Required
External stylesheets are not loaded. All CSS must be inline for reliable rendering across email clients.
CSS Support Limitations
Email clients have significant CSS support limitations compared to web browsers:
Unsupported CSS Features
- Flexbox and Grid layouts
- CSS animations and transitions
- Advanced selectors
- Media queries (limited support)
- External stylesheets
- Pseudo-classes and pseudo-elements
Partially Supported Features
- Basic CSS properties (colors, fonts, spacing)
- Table styling
- Background colors and images (limited)
- Border and padding (with limitations)
Email Client Variations
Different email clients support different CSS features. Gmail, Outlook, Apple Mail, and others each have unique CSS support levels and quirks.
Email Client Modifications
Email clients often modify or rewrite HTML and CSS for security, compatibility, and rendering purposes:
HTML Stripping
Clients may remove or modify HTML elements they consider unsafe or unsupported, changing email appearance.
CSS Rewriting
Clients may rewrite, move, or modify CSS styles, converting external styles to inline or removing unsupported properties.
Image Handling
Clients may block images by default, resize images, or modify image attributes, affecting email layout and appearance.
Link Modifications
Clients may modify links for security (adding tracking, rewriting URLs) or add security warnings.
Content Filtering
Clients may filter or modify content they consider suspicious, potentially changing email appearance or functionality.
Ensuring Consistent Rendering
To ensure consistent email rendering across clients:
1. Use Table-Based Layouts
Use HTML tables for layout instead of CSS-based layouts. Tables are more reliably supported across email clients.
2. Inline All Styles
Use inline CSS styles instead of external stylesheets. Inline styles are more reliably supported.
3. Test Across Clients
Test emails in multiple email clients (Gmail, Outlook, Apple Mail, etc.) to verify consistent rendering.
4. Validate HTML
Validate HTML code using our HTML validator to check for errors and compatibility issues.
5. Use Email-Specific Techniques
Follow email HTML best practices and use email-specific coding techniques designed for email client compatibility.
6. Provide Plain Text Fallback
Always include a plain text version of emails for clients that don't support HTML or for accessibility.
7. Keep It Simple
Use simple, straightforward HTML and CSS. Complex layouts and advanced features are more likely to break across clients.
