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Free HTML check

Email template tester

Paste the HTML. This checker tells you what will go wrong before you send: size, preheader, unsubscribe, links, and alt text.

0 bytes

The HTML stays in your browser. Link and image addresses are requested so a 404 shows up here.

Report

The report lands here.

Paste one email. You get the clip size, the inbox line, and which addresses do not open.

Paste one file

This is an HTML email checker for a file you already have. Drop a .html file or paste the source. The HTML stays in the browser. Link and image addresses are requested, so a 404 shows up here.

It is the same job as an email template tester: you want a verdict on this template, not a new layout. Subject is optional. It is used to see whether the preheader just repeats it.

What the check looks for

Gmail clips HTML past 102,000 bytes. A missing hidden preheader lets the inbox show “View in browser” or whatever text comes first. A footer that says unsubscribe still fails if the link is hidden, the href is #, or the tag belongs to a different ESP. Each http address is requested. A 404, a dead image, and an image over 1 MB are listed with the status. An img without an alt attribute fails a screen reader. An unclosed link or table, or an if without an endif, is listed too.

The focused pages go deeper on one of those: the Gmail clipping checker, the preheader checker, and the unsubscribe link checker.

What this does not do

It does not screenshot Gmail, Outlook, or Apple Mail. The preview frame is your HTML, nothing else. A site that answers 403 blocked the check; that is not the same as a 404. A spam score is a different test.

One pasted file is also not a campaign in three languages. Email template checker is the in-app check: the same kind of mechanical pass, on every translation, before you push to Mailchimp, Klaviyo, Brevo, HubSpot, ActiveCampaign, or Omnisend.

Questions

Do I need an account?

No. Paste the HTML and read the result. The HTML is not uploaded. The addresses in it are requested so a dead link can be shown. An EmailStitch account is only for checking every language in a workspace and pushing the file to an ESP.

Is an email template tester the same as a render preview?

No. A render preview shows the layout in a client. This page flags mechanical problems in the HTML: size, preheader, unsubscribe, links, images, and lang. The frame under the result is your HTML, not a screenshot from Gmail or Outlook.

Will it find a broken link that 404s?

Yes. Each http and https address is requested. A 404 or a name that does not resolve is listed. A 403 means the site blocked the check, so that address is not called broken. href="#", javascript:, and a relative path are caught before any request.