Mailchimp · Brevo · Outlook · Gmail · Apple Mail

Paste your HTML template code and get a full audit: structure, unsupported CSS, images, links, WCAG accessibility, spam signals and compatibility with all major email clients. With real-time code highlighting of problematic sections.

Email template HTML code
📄
Drop the HTML file here
critical warning info
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Paste your HTML template
and run the audit
The report will show each issue with explanation, client impact and suggested fix

Email template compatibility is one of the most underestimated technical challenges in email marketing: a template that looks perfect in preview can break completely in Outlook, get clipped by Gmail or land in spam for structural reasons that are hard to spot without dedicated tools. Outlook uses Word's rendering engine — not a browser — which means flexbox, grid, CSS variables and animations are simply ignored. Gmail clips emails that exceed 102KB, hiding the footer with the unsubscribe link. Spam filters penalise templates with insufficient text, images missing alt attributes and insecure links. With this auditor you can: — Detect structural issues (missing DOCTYPE, non table-based layout, non-inline styles) — Identify CSS properties incompatible with Outlook, Gmail Android and Yahoo Mail — Check WCAG accessibility applied to email (alt text, font size, lang attribute, role) — Scan for spam signals in text and code — Verify HTML file size against Gmail's 102KB limit — See issues highlighted directly in the source code The report assigns a score from 0 to 100 with an A/B/C/D grade and shows the affected client for each issue. Supports standard HTML templates, ESP-ready templates (Mailchimp, Brevo, Klaviyo, HubSpot) and files imported via drag & drop. Keywords: HTML email template audit, email client compatibility checker, Outlook Gmail email template validator, HTML email WCAG accessibility, email marketing spam analysis.