HTML Email Inliner

Email clients are stuck in the 2000s: Gmail strips most style tags, Outlook on Windows ignores half of modern CSS, and Apple Mail handles things just differently enough to break your layout. The only safe path that has worked for fifteen years is inline styles — every rule attached directly to the element it targets, via the style attribute. Writing that by hand is miserable, and copy/pasting from a styled HTML draft never produces the same result twice.

Our HTML Email Inliner closes that gap. Drop in the HTML you already wrote — with utility classes, a Tailwind v4 theme block, or hand-rolled CSS — and we render it inside an isolated iframe, resolve every matching declaration and CSS variable to its final value, then walk the tree and write the resolved styles inline on each element. The result is a portable, self-contained HTML snippet that renders the same way in every major email client, without you maintaining two versions of the template.

Modern web browsers happily honor external stylesheets, CSS custom properties, flexbox, grid and cascade layers — but email is not the modern web. Gmail's web client wraps your markup, mobile Outlook collapses media queries, and corporate Outlook on Windows runs your HTML through Microsoft Word's rendering engine. Across that landscape, the one rendering path that survives is the inline style attribute. CSS inlining is how every transactional email from Stripe, Linear, Notion and Vercel reaches the inbox looking the way the designer drew it.

That is why a CSS to inline converter is a non-negotiable step in any production email pipeline. Whether you build templates in MJML, React Email, Maizzle, or you just write raw HTML with Tailwind utilities, you need an inliner at the end of the chain. Our tool gives you that step as a free, browser-based utility: paste your HTML, optionally drop in your Tailwind theme and custom CSS, toggle whether you want classes preserved and whether unsupported properties (display: grid, gap, transform, animations) should be stripped, and copy the email-ready HTML straight into your sender.

Our HTML email CSS inliner runs entirely in your browser. The Tailwind v4 runtime compiler, the style resolution step, the inlining pass and the preview iframe all execute on your machine, which means private design work and unreleased campaign copy never leave your computer. There is no signup, no rate limit, no watermark on the output, and no server log of the HTML you process. It is the same posture as opening a local devtool — but with a polished UI on top.

Engineers love it for converting React Email and MJML output into a cleaner, hand-auditable form, and for trimming Tailwind utility bloat down to a deterministic inline style payload. Marketers and designers use it to drop a styled HTML mock from Figma-to-code tools into a working inbox-ready template without learning the email-CSS quirks. Customer-success teams paste a one-off transactional snippet, flip the “Remove unused styles” toggle to strip flex/grid/animation rules, and copy the result straight into Customer.io, Postmark, Resend or SendGrid.