CSS Autoprefixer Online
This free CSS Autoprefixer Online tool adds the vendor prefixes your CSS
still needs — -webkit-, -moz-, -ms-, and
-o- — for consistent cross-browser rendering. Paste your CSS into the box
above and the prefixed output appears within a fraction of a second: no npm install, no
build step, nothing to configure. Everything runs locally in your browser, so nothing you
paste is ever uploaded anywhere.
What This CSS Autoprefixer Does
Under the hood, this tool runs the same PostCSS and Autoprefixer engine that powers build tools like webpack and Vite plugins — just without the install, the config file, or the terminal. It reads your CSS, checks each property against current browser support data, and adds exactly the prefixes that property still needs for the browsers you're targeting. Properties that no longer need a prefix anywhere are left alone, so the output never carries dead, unnecessary code.
display: flex;
user-select: none;
}
After .box {
display: flex;
-webkit-user-select: none;
-moz-user-select: none;
user-select: none;
}
How to Add Vendor Prefixes to Your CSS
- Paste or type your raw CSS into the input box.
- The prefixed output updates automatically a moment after you stop typing — there's no button to press.
- Tap Copy above the output to copy the prefixed CSS to your clipboard.
If a rule has a syntax error, a small notice appears and the last valid output stays on screen — fix the syntax above and prefixing resumes automatically.
Setting a Custom Browser Target
By default, this tool targets a broad, modern set of browsers (Autoprefixer's standard
"> 0.5%, last 2 versions" query). If your project supports a narrower or different set
of browsers, type your own browserslist query into the Browser Target
field — the same syntax used in a project's .browserslistrc file or
package.json. A few examples:
last 2 versions— the last two releases of every major browser> 1%— browsers with more than 1% global usageSafari >= 9— Safari 9 and every version after itdefaults— Autoprefixer/browserslist's own broad default set
A narrower, older target adds more prefixes since more browsers need them; a modern-only target adds fewer, sometimes none at all — unlike a plain vendor-prefix generator, this one updates live as you type instead of waiting for a button press.
Frequently Asked Questions
What is Autoprefixer used for?
Autoprefixer adds the vendor-specific prefixes — -webkit-,
-moz-, -ms-, and -o- — that some CSS properties
still need to work consistently across browsers, based on real usage data instead of
guesswork. It saves you from memorizing which properties need which prefixes and from
shipping prefixes that are no longer needed for browsers that already support the
unprefixed property.
What are CSS vendor prefixes?
Vendor prefixes are short tags — -webkit- (Chrome, Safari, newer Edge),
-moz- (Firefox), -ms- (old Edge/IE), and -o- (old
Opera) — that browser makers add in front of an experimental CSS property name while
it's still evolving. Once a property is fully standardized every browser drops the
prefix, but older and some current browsers still need it for a handful of properties
like user-select and backdrop-filter.
Is Autoprefixer still needed?
Yes, for a shrinking but real set of properties. Most CSS written today needs no
prefixes at all, but a few — user-select, backdrop-filter, and
some newer properties in their early support window — still render inconsistently
without one on at least some browser your visitors use. Autoprefixer only adds a prefix
a property genuinely still needs for your chosen browser target, so it never pads your
CSS with dead weight.
What is a browserslist query?
A browserslist query is a short text string — like "> 1%, last 2 versions" or "Safari >= 9" — that describes which browsers you need to support. Autoprefixer reads it to decide exactly which prefixes your CSS needs: a narrower, older target adds more prefixes, while a modern-only target adds fewer or none.
What's the difference between this and the official Autoprefixer demo?
Both run the same Autoprefixer engine and produce identical output. This tool adds a cleaner, mobile-friendly interface, a debounced live preview as you type, and a one-tap copy button — with nothing to install and nothing you paste ever leaving your device.
