HTML Email Validator
Validate your HTML email code for compatibility across different email clients
Enter your HTML code and click "Validate HTML" to see the analysis
This page provides original, human-reviewed information about validating HTML email markup, explaining the subset of HTML and CSS that major clients support and how to fix common rendering breakages.
HTML email validation ensures your email campaigns render correctly across different email clients and devices. Unlike web browsers, email clients have varying levels of HTML and CSS support, making validation crucial for successful email marketing.
What We Validate:
- HTML Structure:Proper DOCTYPE, semantic markup, and tag nesting
- CSS Support:Inline styles, supported properties, and fallbacks
- Images:Alt attributes, dimensions, and accessibility
- Links:Proper formatting, tracking parameters, and accessibility
- Table Layout:Email-safe layout structures
- Media Queries:Responsive design compatibility
- Text Content:Text-to-image ratio for deliverability
HTML Structure:
- Use table-based layouts for maximum compatibility
- Include proper DOCTYPE:
<!DOCTYPE html> - Set explicit width and height attributes on images
- Use inline CSS instead of external stylesheets
- Include alt text for all images
- Use absolute URLs for all links and images
CSS Guidelines:
- Avoid CSS Grid and Flexbox (limited support)
- Use web-safe fonts with fallbacks
- Keep CSS simple and inline when possible
- Use media queries sparingly and with fallbacks
- Avoid CSS shorthand properties
- Test background images with fallback colors
Content Guidelines:
- Maintain a good text-to-image ratio (60:40 or better)
- Keep email width between 600-800px
- Use preheader text effectively
- Include a clear call-to-action
- Provide a plain text version
High Compatibility Clients:
Limited Compatibility Clients:
Uses Word rendering engine, limited CSS support
Strips some CSS properties, limited media query support
Better than desktop Outlook but still has limitations
Common Issues by Client:
- Outlook:No support for CSS Grid, Flexbox, or background images on divs
- Gmail:Strips CSS from <head> section, use inline styles
- Yahoo:Limited media query support, may strip some CSS
- Mobile clients:Varying viewport handling and touch target sizes
Why do my emails look different in different clients?
Email clients use different rendering engines and have varying levels of HTML/CSS support.Unlike web browsers that follow web standards, email clients prioritize security and performance over rendering fidelity.
Should I use tables or divs for email layout?
Use tables for the main layout structure as they have the best cross-client compatibility.You can use divs for content within table cells, but avoid complex div-based layouts.
How do I make my emails responsive?
Use media queries with fallbacks, fluid tables, and scalable images.Test thoroughly as media query support varies significantly between clients.
What's the best way to handle images in emails?
Always include alt text, set explicit dimensions, use absolute URLs, and provide fallback colors for background images.Many clients block images by default.
How often should I validate my email HTML?
Validate every new template and after significant changes.Also validate when you notice rendering issues or before important campaigns.
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