Free email HTML checker. See where your email breaks before your readers do.
Runs in your browser. Nothing is uploaded.
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About
What Stampcheck is
A free tool for marketers and email developers. Paste the HTML of an email and see, in seconds, what will break in Gmail, Outlook, Apple Mail and on phones before it reaches real inboxes.
What it checks
Rendering: styles Gmail and Outlook drop, Outlook button and padding problems, missing font fallbacks, image formats, Gmail's clipping and style limits
Phones: width on small screens, missing mobile rules, tiny text, iOS auto-links
Links and images: dead, insecure, shortened or mismatched links, broken image addresses, missing alt text
Accessibility: language, contrast, layout tables, headings, link text
Deliverability and compliance: unsubscribe link, postal address, preview text, subject, placeholder text, spam triggers
How it works
Everything runs in your browser. Your HTML is never uploaded, so you can check unreleased campaigns safely. Previews approximate each client; always send yourself a test before a campaign goes out.
Last updated 28 October 2026
Your email stays on your device
Stampcheck checks your HTML inside your browser. The HTML you paste, type or open is never sent to us or to anyone else, and it is gone when you close the tab.
What we keep in your browser
If you edit the sender name or address in the preview, or resize the panels, those settings are remembered in your browser so you don't have to set them again. They never leave your device, and clearing this site's data removes them.
What we count
We count anonymous usage events, such as how many checks run and which buttons are used, so we know what to improve. These counts never include your HTML or anything that identifies you. We don't use cookies and we don't track you across sites.
Hosting
Our hosting provider keeps standard server logs, such as IP address, browser type and time of visit, to keep the site running and secure. We don't combine these logs with other data. Fonts and graphics are part of this page, so no other company is contacted when you use it.
Your rights
Because the tool doesn't collect personal data, there is nothing for us to access, correct or delete. If you have a question about server logs or your rights under GDPR or KVKK, contact us using the details on the Contact page.
Changes
If we start handling data differently, for example to offer automatic fixes, we will update this page before that change goes live.
Last updated 28 October 2026
Using Stampcheck
Stampcheck is free to use for personal and commercial work. By using it you agree to these terms.
Your content
The HTML you check stays yours. It is processed in your browser and we don't receive it. Only check content you have the right to use.
Fair use
Don't use the site to break the law, to harm the service or other people, or to try to get around its security.
No guarantee
Stampcheck is provided as it is. The checks follow known rendering rules but email clients change often, so we can't promise that every problem is found or that every result is correct. Test your email before sending it.
Liability
To the extent the law allows, we are not responsible for losses that result from using the site or relying on its results, such as a campaign that renders badly.
Changes and law
We may update these terms and will change the date above when we do. These terms are governed by the laws of the Republic of Türkiye.
Gmail, Outlook and Apple Mail are trademarks of their owners. Stampcheck is an independent tool and is not affiliated with them.
Last updated 28 October 2026
No cookies
Stampcheck doesn't set cookies. There is no tracking, no advertising and no cookie banner, because there is nothing to consent to.
Browser storage
The only things kept in your browser are the sender name and address you type into the preview and your panel sizes, so the tool remembers them next time. Nothing is sent anywhere.
If this changes
If we ever add a feature that needs cookies, we will list them here and ask for your consent first where the law requires it.
Get in touch
Found a check that's wrong, a client we should cover, or a bug? We read every message.