How modern is your CSS?
Enter a website or drop in your project. See the modern CSS it already uses, the old techniques it still carries, and the modern way to replace each one.
Your own files never leave your computer.
Check how modern a site is
We fetch the page and its stylesheets, the same public files any visitor gets. Nothing is kept.
How it works
Private, up to date and free.
- 1
Drop in your project
A folder, some files, pasted CSS or a website address. Your files are checked in this page and never uploaded.
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See what's safe to ship
Each finding links to the modern version and shows its Baseline status, checked daily. Pick your target to see which need a fallback.
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Watch the numbers fall
With a free account, save each run to a project and compare it with the last one as you migrate.
How modern is the web?
The audit on well-known sites, checked every week.
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MDNdeveloper.mozilla.org · Reference93%Uses @property, :focus-visible, :is(), :where(), :has() and 9 moreStill has Negative-margin gutters - 02
Shopifyshopify.com · Tech81%Uses <dialog> and popover, Scroll-driven animations, Anchor positioning, text-wrap: balance, pretty and 17 moreStill has [dir=rtl] overrides, Negative-margin gutters, translate(-50%, -50%) centering and 2 more - 03
GitHubgithub.com · Tech76%Uses <dialog> and popover, Scroll-driven animations, Anchor positioning, field-sizing and 18 moreStill has Floats and clearfix, Negative-margin gutters, font-size: 0 whitespace hack and 4 more - 04
Vercelvercel.com · Tech76%Uses <dialog> and popover, @starting-style, field-sizing, accent-color and 18 moreStill has Floats and clearfix, Negative-margin gutters, font-size: 0 whitespace hack and 4 more - 05
Tailwind CSStailwindcss.com · Developer tools75%Uses @starting-style, field-sizing, accent-color, text-wrap: balance, pretty and 17 moreStill has [dir=rtl] overrides, Floats and clearfix, Negative-margin gutters and 4 more
Save your reports, track your progress
Run the audit without an account. Create a free one to save runs to projects, mark suggestions done or keep them as is, follow your progress on the dashboard and open a lesson for every suggestion: the modern version, how browsers got there and when the old way is still right.
Open your dashboardQuestions
Is my code uploaded?
No. Your files are read and checked by this page, in your browser. Nothing is sent to our server. If you save a run to a project, only the numbers and the name you give it are saved, never your code.
How is the modernity score worked out?
It weighs the modern CSS a project uses against the old techniques it still carries. Each one counts once, however often it appears, so one big generated file can't swing the score.
Can it check a live website?
Yes. Enter the address and our server fetches the page and its stylesheets, the same public files any visitor gets, and hands them to the audit in your browser. It reads every linked stylesheet (up to 25), the files they @import, <style> blocks and style attributes. Nothing is kept. Sites behind a login, and CSS added later by JavaScript, aren't included.
Which files does it check?
CSS, SCSS, Sass and Less files, JavaScript and TypeScript, package.json, and templates such as HTML, PHP, Astro, Twig and JSX. It skips node_modules, .git and build folders, and any single file over 2 MB.
How accurate is it?
Every match comes with its file and line, so you can check it yourself. It looks for patterns, so some matches are fine to keep, such as a float that wraps text around an image. You can ignore those, and they stay ignored in this browser.
What does Baseline mean here?
Baseline says which features work in every major browser. Each fix shows its status, from web-features and MDN's browser data, checked daily. Widely available means it has worked everywhere for at least 30 months.
Do I need an account?
No, not to run it: every check, every match and the exports work without one. A free account lets you save runs to projects, mark suggestions done or keep them as is, see your progress on the dashboard and open a lesson for every suggestion.
Is it really free?
Yes. The whole site is free. It's paid for by the newsletter's sponsors and the sponsor slot on each page.
See what your CSS is carrying
It takes one drop. Nothing is uploaded and no account is needed.
Audit your CSS