Free Email Tool

HTML Email Tester and preheader previewer

Paste your email HTML and see it render instantly in desktop and mobile, light and dark, with a real inbox row showing your sender, subject, and preheader exactly as Gmail and Apple Mail display them. No signup, no test send.

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Inbox preview

Gmail (desktop)desktop
Y
Your Company9:41 AM
Your trial ends in 3 days
You have used 47% of your credits this month.
Apple Mail (iPhone)mobile
Y
Your Company9:41 AM
Your trial ends in 3 days
You have used 47% of your credits this month.
·

Rendered email

Rendered locally in a sandboxed frame. No scripts run, nothing is sent, nothing is stored.

The forgotten line

Your preheader is a second subject line

Every inbox shows two lines of copy before anyone opens your email: the subject and the preheader (also called preview text). Most people obsess over the subject and leave the preheader on autopilot, which is why so many emails show "View this email in your browser" or a naked link right in the inbox.

Treat the preheader as an extension of the subject, not a repeat of it. If your subject is "Your trial ends in 3 days", the preheader should add the next beat: "Keep your workspace and everything you built". Together they read like one thought. Use the inbox preview above to see both together, and where each client cuts them off.

What breaks in real inboxes

The rendering problems this preview catches

  • Dark mode contrast. Apple Mail and the Gmail app recolor light backgrounds. Near-black text on a card can vanish. Toggle the dark background to check.
  • Mobile width. A layout that looks fine at 680px can overflow at 390px. Switch to mobile to see if columns stack or text gets cramped.
  • Missing preheader. Leave preview text empty and the client scrapes your first line. The preview shows you exactly what that looks like.
  • Truncation. A red ellipsis marks where each client cuts your subject or preheader. Front-load the words that matter.
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FAQ

HTML email testing questions

An HTML email tester lets you paste your email's HTML and see it rendered exactly as it would look in a real inbox, without sending a test email to yourself. This tool renders your HTML in a sandboxed frame with desktop and mobile widths, light and dark backgrounds, and a live inbox row showing your sender, subject, and preheader.