No. 05 · HTML email preview

HTML email preview

Paste your email's HTML to see it at desktop and phone widths, in simulated dark mode and with images blocked. A lint list flags the things mail apps strip, and a size meter warns before Gmail clips it.

Your HTML

Or drop an .html file

Size

0 KBGmail clips at about 102 KB

Checks

    Preview

    Desktop, light, images on

    Scripts, forms and plugins never run in this preview. Links open in a new tab.

    How to test an HTML email

    Paste the complete HTML of your campaign or transactional email, or drop the .html file your editor exported. Switch between Desktop and Phone to check that your layout collapses properly at 375 pixels, try both dark-mode simulations (Dark uses your own prefers-color-scheme styles, Dark, inverted flips every colour), and tick Block images to see what readers get before they click "show images".

    What the checks look for

    • Errors: relative URLs (they break in every inbox), scripts, external stylesheets and HTML over Gmail's clipping size.
    • Warnings: images without alt text or width/height, http images, data: URIs, flexbox, grid, positioning and CSS variables, missing preheader text, empty links and image-only layouts.
    • Notes: doctype, charset, viewport, lang and title, layout tables without role="presentation", web fonts, and a reminder to send a plain-text part too.

    Merge tags from common sending platforms, such as {{unsubscribe_url}} or *|ARCHIVE|*, are not reported as broken links.

    Ready for the real thing? A browser preview cannot show what a mail server does to your message. Send a test to a free temporary inbox on CleanTempMail to see how it actually arrives, without cluttering your own mailbox.

    Testing in a pipeline? The CleanTempMail Temp Mail API is built for automated email and verification testing, with no subscription.

    Questions

    Is it safe to paste an email I received?

    The preview runs in a sandboxed frame with scripts, forms and plugins disabled, so nothing in the email can run code. Remote images do load, which tells the sender's server that the email was opened, so switch on Block images first if that matters to you.

    How accurate is the dark mode preview?

    It is an approximation. Dark applies your email's own prefers-color-scheme: dark styles and darkens anything without colours of its own, roughly what Apple Mail does. Dark, inverted flips every colour, like the Gmail app on some phones. Real apps each have their own rules, so always send a test.

    Why does Gmail clip emails at 102 KB?

    Gmail cuts off the HTML of messages larger than about 102 KB and shows a View entire message link. Anything after the cut, often including the unsubscribe link and tracking, is hidden until the reader clicks it.

    Does the preview look exactly like Outlook?

    No. This preview uses your browser's engine. Classic Outlook for Windows uses Microsoft Word to render email and ignores a lot of modern CSS. The lint list flags the most common things it drops.