HTML Email Linter

Find broken tags before Outlook does.

A free HTML email linter that catches the bugs only email clients care about — unclosed tags, broken table nesting, and Outlook-specific rendering traps. Paste your HTML, get a line-by-line breakdown.

Open the linterBeautify first

Why email needs its own linter

Email clients are not browsers. Gmail strips your <style> tag. Outlook ignores border-radius. Yahoo flattens your CSS-grid layout to a single column. The W3C HTML validator does not know any of this — it tells you your HTML is fine, then you ship and Outlook breaks the layout.

EMLinter's HTML email linter is rule-tuned for these clients. It flags broken table nesting (the #1 cause of Outlook layout collapse), unclosed tags (the #1 cause of "everything below this looks broken" bugs), missing image alt text (deliverability + accessibility), and the patterns email clients specifically choke on. It is the validator you'd use if you were writing a coding standard for an email-development team.

HTML Email Linter FAQs

A purpose-built HTML email linter checks for unclosed and mismatched tags, broken table nesting, missing alt attributes on images, missing role="presentation" on layout tables, and Outlook-specific bugs like <div> inside <td> or unsupported CSS properties. Browser-grade validators miss most of these because they only check generic HTML5.
A regular HTML validator (like the W3C tool) enforces HTML5 spec compliance — useful for websites, mostly irrelevant for email. Email clients use 1999-era rendering engines, strip CSS aggressively, and break on patterns modern browsers accept. EMLinter's linter is rule-tuned for email, not the web.
It eliminates the most common rendering bugs — broken layouts from malformed tables, mysterious gaps from unclosed tags, Outlook-only formatting failures. For a true render guarantee, also use the dark-mode tester and the Outlook generators on this site, then send yourself a test through your own email platform before you ship.
Yes. The "Beautify & Validate" button runs both steps in sequence: format the code into clean indentation, then run the validator on the cleaned version. Helpful when you're working with minified or copy-pasted templates where errors are hard to spot.
Yes. Conditional comments and VML blocks are recognized and excluded from standard tag-pair validation — they're intentionally malformed to non-Outlook clients, so flagging them would be a false positive.
Never. The linter runs 100% in your browser. Your code, including any unreleased campaigns, never leaves your device. Same goes for the beautifier, minifier, dark-mode tester, and Outlook generators on this site.