Free HTML email tester for Outlook, Gmail & mobile
Email clients are notoriously inconsistent: Outlook renders with Microsoft Word's engine, Gmail clips messages over 102 KB and strips large <style> blocks, and mobile apps reflow your layout. This email template tester lints your raw HTML against the rules that actually break real campaigns, gives you a compatibility score, previews the result on desktop and mobile, and auto-fixes the issues that can be safely automated — all 100% in your browser, with no signup and nothing uploaded.
What it checks
- Gmail clipping — flags emails over the 102 KB threshold that triggers "[Message clipped]".
- Gmail style limit — warns when <style> blocks exceed 16 KB.
- Outlook killers — Flexbox/Grid, position, float, margin and border-radius.
- Images — missing width/height attributes and missing alt text.
- Scripts & semantic tags — stripped or unreliable across clients.
- Shorthand hex colors that some webmail clients ignore.
Who it's for
- Email developers debugging Outlook and Gmail rendering before sending.
- Shopify & e-commerce teams testing Liquid notification and marketing templates.
- Marketers using Mailchimp, Klaviyo or SFMC who want to validate merge-tag emails.
- Agencies QA-ing client templates without pasting confidential HTML into a server.
Test Shopify Liquid & templated emails
Unlike a plain HTML validator, this tester understands templating languages. Paste a Shopify Liquid, Handlebars, Jinja or merge-tag email and it renders the real output with editable sample data — so the lint and preview reflect what your subscribers actually receive. Undefined variables fall back to showing their name, and empty loops keep a placeholder row, so the layout never collapses while you work.
Frequently asked questions
What is an HTML email tester?
An HTML email tester analyzes your email's HTML and CSS for rendering problems across clients like Outlook, Gmail and Apple Mail. This tool lints your code, scores its compatibility, previews how it looks on desktop and mobile, and suggests fixes — all in your browser.
Is this email template tester free?
Yes — completely free with no signup, no account and no usage limits. Everything runs locally in your browser using the native DOMParser API.
Which email clients does it check compatibility for?
It targets the issues that most often break in Microsoft Outlook (which uses the Word rendering engine), Gmail and Google webmail (including the 102 KB clipping threshold and 16 KB style-tag limit), and mobile clients — flagging Flexbox/Grid, CSS positioning, margins, border-radius, unsupported semantic tags, scripts, and images missing dimensions or alt text.
Can I preview Shopify Liquid email templates?
Yes. It renders Shopify Liquid, Handlebars, Jinja and ESP merge-tag syntax (such as Mailchimp *|FNAME|*) using editable sample data, so you can lint and preview the real output. Variables you have not defined fall back to showing their name so the layout stays intact.
Does it send my email HTML to a server?
No. The tool is 100% client-side. Your HTML never leaves your browser — there is no backend, no upload and no tracking of your content. Scripts in your template are never executed; the preview runs in a sandboxed iframe.
What does the Auto-Fix feature do?
It deterministically rewrites the issues that can be safely automated: expanding shorthand hex colors, removing script tags, converting HTML5 semantic tags to divs, adding missing alt attributes, and promoting CSS pixel dimensions to width/height attributes on images. Structural problems like Flexbox-to-table conversion are left for manual work.