Free CSS Prefixer Online

Add vendor prefixes to your CSS automatically in your browser.

Input CSS

Prefixed CSS

CSS Prefixing Examples

Vendor prefixes ensure cross-browser support. Example:

Flexbox and transforms

Input (no prefixes):

Input

Prefixed output:

Output

Use Sample above to load more example data.

What Is a CSS Prefixer?

You wrote clean, standards-compliant CSS, but then tested in Safari 14 and everything broke. Sound familiar? Vendor prefixes like -webkit-, -moz-, and -ms- exist because browsers sometimes ship experimental CSS features before the spec is final. A CSS prefixer adds these automatically so you don't have to remember which properties need them. The W3C CSS specifications define the standard, while Can I Use tracks real-world browser support for each property.

This tool parses your CSS and adds vendor prefixes where needed. It runs entirely in your browser. Nothing is sent to a server. Modern browsers need fewer prefixes than before, but some properties (e.g. user-select, display: flex in older Safari) still benefit. For formatting, use the CSS Formatter. For minifying, use the CSS Minifier.

How to Use This Tool

1

Paste or Upload CSS

Copy your CSS and paste it into the left editor. You can also click Upload to load a .css file. The Sample button loads example data. Invalid CSS will show an error.

2

View the Prefixed Output

The right panel shows CSS with vendor prefixes added. Properties like display: flex, user-select, and transform get the appropriate prefixes for older browsers.

3

Copy or Download

Use Copy or Download. For SCSS or Less, compile first with SCSS to CSS or Less to CSS, then prefix. For validation, use the CSS Validator.

When CSS Prefixing Helps

When supporting older browsers (Safari, older Chrome, legacy IE) or using newer CSS features that aren't fully standardized, prefixing ensures compatibility. Build tools like Autoprefixer or PostCSS often handle this in production, but this tool is useful for one-off files, quick checks, or when a build step isn't available.

Email CSS, embedded styles, or CDN-hosted CSS may need manual prefixing. Running your stylesheet through here gives you browser-ready output. For converting to inline styles (e.g. for email), use CSS to Inline after prefixing.

Frequently Asked Questions

Do I still need CSS vendor prefixes?

It depends on your target browsers. Most modern browsers have dropped the need for prefixes on common properties, but older Safari, iOS WebKit, and some mobile browsers still require them for things like backdrop-filter and user-select. Check Can I Use for specific properties.

How is this different from Autoprefixer?

Autoprefixer runs inside a build pipeline (PostCSS, webpack, Vite). This tool runs directly in your browser with no setup — just paste CSS and get prefixed output. It's perfect for one-off files, quick checks, or when you don't have a build step.

Is my CSS sent to a server?

No. All prefixing happens locally in your browser using JavaScript. Your CSS never leaves your machine, so it's safe to use with proprietary stylesheets or production code.

Which CSS properties get prefixed?

The tool targets commonly-needed prefixes: flexbox properties, transforms, transitions, user-select, backdrop-filter, gradients, and more. The MDN vendor prefix docs explain which browsers use which prefixes.

Related Tools

CSS Formatter CSS Minifier CSS Validator CSS to Inline SCSS to CSS Less to CSS CSS to SCSS CSS to Less JSON Formatter

For the CSS specification, see W3C CSS. MDN CSS is the reference. Can I Use tracks browser support. Autoprefixer for build pipelines.