# MailViewr

> Free HTML email preview and testing tool. See how your emails render across Gmail, Outlook, Apple Mail, and mobile — before you hit send.

MailViewr is a browser-based tool that lets developers, marketers, and designers preview and test HTML emails across major email clients. No signup, no downloads — paste your HTML and see instant results.

## Core Tools

- [Email Preview Tool](https://www.mailviewr.com/email-preview): Paste HTML and preview how it renders across Gmail, Outlook, Apple Mail, Yahoo, and mobile clients. Includes dark mode testing, compatibility scoring, and device simulation.
- [Email Builder](https://www.mailviewr.com/email-builder): Drag-and-drop email builder with real-time preview. Build responsive emails visually — no coding needed. Export clean HTML for any ESP.
- [Free Email Templates](https://www.mailviewr.com/templates): Ready-to-use, responsive email templates — newsletter, promotional, welcome, transactional, event, and announcement.

## Template Library

- [Newsletter Template](https://www.mailviewr.com/templates/newsletter-template-email-preview): Professional newsletter email layout with responsive design.
- [Promotional Template](https://www.mailviewr.com/templates/promotional-template-email-preview): Bold promotional template for sales and limited-time offers.
- [Welcome Template](https://www.mailviewr.com/templates/welcome-template-email-preview): Engaging first-email template for new subscribers.
- [Transactional Template](https://www.mailviewr.com/templates/transactional-template-email-preview): Clean template for order confirmations, receipts, and notifications.
- [Event Invitation Template](https://www.mailviewr.com/templates/event-template-email-preview): Eye-catching template for webinars, conferences, and launches.
- [Announcement Template](https://www.mailviewr.com/templates/announcement-template-email-preview): Template for product launches, feature releases, and company updates.

## Blog & Guides

- [Email Development Blog](https://www.mailviewr.com/blog): Tutorials, tips, and best practices for HTML email development.
- [Ultimate Guide to HTML Email Testing](https://www.mailviewr.com/blog/ultimate-guide-html-email-testing): Complete guide covering Gmail, Outlook, responsive design, CSS compatibility, and rendering issues.
- [HTML Email Best Practices for 2026](https://www.mailviewr.com/blog/html-email-best-practices): Essential techniques for creating emails that render perfectly across all clients.
- [How to Preview HTML Email in Gmail](https://www.mailviewr.com/blog/how-to-preview-html-email-in-gmail): Step-by-step guide to test Gmail rendering on desktop and mobile.
- [How to Test Email Rendering in Outlook](https://www.mailviewr.com/blog/how-to-test-email-rendering-in-outlook): Guide to Outlook's Word rendering engine and fixing common issues.
- [Gmail vs Outlook Rendering Differences](https://www.mailviewr.com/blog/gmail-vs-outlook-email-rendering-differences): Compare CSS support and rendering behavior between the two largest email clients.
- [Email Width Best Practices](https://www.mailviewr.com/blog/email-width-best-practices): Ideal email widths, responsive breakpoints, and client viewport handling.
- [Responsive Email Template for Newsletters](https://www.mailviewr.com/blog/responsive-email-template-for-newsletters): Build responsive newsletter templates with a free drag-and-drop builder.
- [Email Safe Fonts Guide](https://www.mailviewr.com/blog/email-safe-fonts-guide): Which fonts work in email, web font fallbacks, and client-specific rendering.
- [HTML Email Checker](https://www.mailviewr.com/blog/html-email-checker): Free compatibility scanner — get an instant score, error count, and fix suggestions.
- [Email Builder for Small Business](https://www.mailviewr.com/blog/email-builder-for-small-business): Build professional emails with a free no-code drag-and-drop builder.
- [Email Preview Tool for Developers](https://www.mailviewr.com/blog/email-preview-tool-for-developers): Developer-focused preview tool with code editor, compatibility checker, and dark mode testing.
- [How Gmail Rewrites Your Email Colors in Dark Mode](https://www.mailviewr.com/blog/dark-mode-color-transform-email-preview): How we reverse-engineered Gmail's dark mode color algorithm to build 75–80% accurate previews.

## Key Features

- Instant HTML email preview with no signup required
- Email client simulation: Gmail (web, iOS, Android), Outlook (desktop, mobile), Apple Mail, Yahoo Mail
- Dark mode preview and testing
- Compatibility scoring with per-client error detection
- CSS inlining and validation
- Device simulation (desktop, tablet, mobile)
- Drag-and-drop email builder with HTML export
- Free responsive email templates

## FAQ

- [Frequently Asked Questions](https://www.mailviewr.com/faq)

## Optional

- [Full documentation](https://www.mailviewr.com/llms-full.txt)