Any CSS property or value (like display:flex, border-radius or position) or HTML element (like , or ): 300 in all. Start typing and pick from the suggestions to see how it does in all 21 clients.

CSS Support Lookup

Look up any of 300 CSS properties and HTML elements and see where it works, in all 21 clients, from caniemail's data.

@emailens/engine 0.17.2 · data last changed 27 Oct 2026

Try one:

display:flex display:grid border-radius background-image position max-width gap flex-direction linear-gradient <video>

Check a whole email instead: open the checker and paste it there, five clients, no account.

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No signup · Five clients free, Outlook Classic included · All 21 with an account

Which clients need an account

Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, AOL Mail, Fastmail, Superhuman open with a free account.

The checker needs a computer screen.

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Other free tools: CSS Inliner · Dark Mode Simulator · Outlook Ghost Table Generator · Outlook VML Background Generator · Bulletproof Button Generator · Client Targeting Generator · Email Rendering Playground

Run this check on every email

Lint every pull request with the open-source CLI, free: npx @emailens/cli lint email.html (CLI docs).

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Questions

What can I look up?

Any CSS property or value (like display:flex, border-radius or position) or HTML element (like <video>, <picture> or <style>): 300 in all. Start typing and pick from the suggestions to see how it does in all 21 clients.

What do 'partial' and 'untested' mean?

Works means the client renders the feature as expected; not supported means it doesn't. Partial means it works with caveats: only in some contexts, or with a fallback. Untested means caniemail has no record for that client and feature yet, so it never counts for or against the feature.

Why does Outlook Classic fail so many features?

Outlook Classic renders with Microsoft Word, not a browser engine. 51 of 300 features work in Outlook Classic · 26 partial · 222 not supported · 1 untested. display:flex, display:grid, border-radius and linear-gradient are not supported there, which is why table-based layouts and VML fallbacks are still standard for email.

How do I check a whole email at once?

This tool looks up one feature at a time. To check an entire email, paste your HTML into the CSS compatibility checker. It runs every property through the same data and gives you a per-client score plus fixes for what doesn't work.

Get new email CSS fixes by email.