LintMail

About

LintMail audits your email HTML before you hit send — right inside Chrome, with no backend, no API calls, and no data ever leaving your browser.

WHAT IT DOES
Paste, upload, or capture an email's HTML. LintMail runs a static audit across six categories and gives you a weighted score from 0 to 100, with actionable feedback on every failing rule.

AUDIT CATEGORIES
• Accessibility — Alt text, font sizes, WCAG AA real contrast ratios (luminance formula), heading structure, tap target sizes, lang attribute, table role attributes
• Deliverability — Unsubscribe link, spam word patterns, text/image area ratio, email size, link density, redirect chain detection
• Best Practices — Inline CSS, viewport meta, HTML doctype, table-based layout, external CSS, image dimensions
• Email Client Compatibility — CSS properties checked against a Can I Email matrix for Gmail, Outlook, Apple Mail, Yahoo Mail, and Samsung Mail
• Dark Mode — prefers-color-scheme support, hardcoded background colors, image transparency
• Spam Score — SpamAssassin-based patterns, excessive caps, money symbols, hidden text, JavaScript, form tags

KEY FEATURES
→ Campaign type weighting — scores are weighted differently for Promotional, Transactional, Welcome, Abandoned Cart, and Newsletter campaigns. A transactional email gets penalized more for poor accessibility than a promotional one.
→ ESP detection — detects merge tag syntax from 10+ platforms (Mailchimp, Klaviyo, HubSpot, Salesforce Marketing Cloud, Braze, SendGrid, and more) and validates tags are properly closed.
→ Email client compatibility matrix — Gmail, Outlook (2016/2019/365), Apple Mail, Yahoo Mail, Samsung Mail. Version-specific notes included.
→ Live preview — renders the email in a sandboxed iframe with Dark Mode simulation, No Images mode, and a fold line at 600px.
→ A/B comparison — analyze two HTML versions simultaneously with diff scores per category.
→ Analysis history — stores up to 20 runs locally with diff badges between consecutive analyses.
→ Export — JSON (full report), Markdown, PDF (print), Excel (.xlsx).
→ AI summaries — optional. Bring your own API key for Claude, Gemini, or OpenAI. Keys are stored locally and never sent to any LintMail server.
→ Bilingual — English and Brazilian Portuguese.

PRIVACY
LintMail has no backend. Zero. Your email HTML stays in your browser. Analysis history is saved in Chrome's local storage, accessible only to the extension. If you use the optional AI feature, your HTML is sent directly from your browser to the AI provider you chose (Anthropic, Google, or OpenAI) — not to us.

WHO IS IT FOR
Email developers and designers who build or QA HTML emails. Marketing team members who send campaigns and want a quick sanity check. Agency teams with high email volume.