Email Template Previewer

Building HTML emails? Paste your template into HTML Viewer Cat and see exactly how it renders — at phone, tablet, and desktop widths. No need to send test emails, no need to sign up for anything. Just paste and preview.

Why preview emails in a browser?

The traditional email testing workflow is painful: edit the HTML, send a test email, open it on your phone, check your desktop client, repeat. Each cycle takes minutes. With a browser-based previewer, you paste your HTML once and check all viewport sizes in seconds. You can also edit in real time and see the results instantly.

Built-in responsive testing

Most emails are read on mobile. HTML Viewer Cat lets you switch between phone (375px), tablet (768px), and desktop (full width) previews with one click. This is critical for catching layout issues that only appear at certain widths — like images overflowing containers, text wrapping awkwardly, or buttons becoming too small to tap.

What you can test

• Marketing emails — newsletters, promotions, product announcements
• Transactional emails — order confirmations, password resets, welcome emails
• Notification emails — alerts, digests, status updates
• Custom templates — any HTML email template from any platform (Mailchimp, SendGrid, etc.)

Email HTML tips

• Use inline styles — many email clients strip <style> blocks
• Use tables for layout — flexbox and grid are not supported in most email clients
• Set max-width: 600px on your container for the best cross-client experience
• Always include alt text on images — many clients block images by default
• Test at 375px width first — that's where most people will read your email

Privacy

Your email HTML never leaves your browser. Everything is rendered locally in a sandboxed iframe. This makes it safe to preview internal emails, unreleased campaigns, or any template containing sensitive content.