Free CSS Autoprefixer – Add Vendor Prefixes for Browser Compatibility

Automatically add CSS vendor prefixes for maximum browser compatibility. Support for Chrome, Firefox, Safari, Edge, and legacy browsers. Real-time processing with visual prefix indicators. Free, fast, and 100% browser-based.

What Is CSS Autoprefixing?

CSS Autoprefixing is the process of automatically adding browser-specific vendor prefixes to CSS properties that require them for cross-browser compatibility. Different browsers have historically implemented experimental CSS features using their own prefixes before standardization.

Why Are Vendor Prefixes Needed?

When browsers implement new CSS features, they often use vendor prefixes during the experimental phase:

Without these prefixes, certain CSS properties may not work in older browser versions, leading to broken layouts and visual inconsistencies.

The Problem with Manual Prefixing

Manually adding vendor prefixes is:

Time-Consuming: Remembering which properties need which prefixes wastes development time.

Error-Prone: Missing a prefix means broken styling for some users.

Maintenance Nightmare: Prefix requirements change as browsers update—keeping track is impossible.

Code Bloat: Prefixed CSS files become 2-3x larger and harder to read.

Our autoprefixer solves all these problems instantly.

How to Use This Tool

Step 1: Paste Your CSS

Enter your standard CSS into the input area. Write clean, unprefixed CSS.

Step 2: Automatic Processing

Prefixes are added in real-time as you type. No buttons to click.

Step 3: Review Results

See exactly which prefixes were added and for which properties.

Step 4: Copy or Download

Copy the prefixed CSS to your clipboard or download as a .css file.

Supported CSS Properties

Our autoprefixer handles 50+ CSS properties across multiple categories:

Transform & Animation

Flexbox Layout

Visual Effects

User Interaction

Typography

Multi-Column Layout

Understanding Vendor Prefixes

-webkit- (WebKit Engine)

Used by browsers built on WebKit and Blink engines:

• Google Chrome (all versions)
• Apple Safari (all versions)
• Microsoft Edge (Chromium-based)
• iOS Safari (all versions)
• Android WebView

This is the most commonly needed prefix as WebKit powers the majority of web traffic.

-moz- (Mozilla/Gecko Engine)

Used by Firefox and other Gecko-based browsers:

• Mozilla Firefox (desktop and mobile)
• Tor Browser
• Waterfox
• Pale Moon

Firefox has excellent standards support, so fewer properties need prefixing.

-ms- (Microsoft/Trident Engine)

Used by legacy Microsoft browsers:

• Internet Explorer 10-11
• Edge (legacy, pre-Chromium)

While IE market share is minimal, enterprise environments often require support.

-o- (Opera/Presto Engine)

Used by Opera before switching to Blink (2013):

• Opera 10-12

Rarely needed today as Opera now uses Blink (WebKit-compatible).

CSS Autoprefixing Best Practices

Write Standard CSS First

Always write standard, unprefixed CSS and let tools add prefixes:

/* Write this */
.element {
  transform: rotate(45deg);
  transition: all 0.3s ease;
}

/* Tool generates this */
.element {
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
  -webkit-transition: all 0.3s ease;
  -o-transition: all 0.3s ease;
  transition: all 0.3s ease;
}

Keep Standard Property Last

The unprefixed property should always come last, acting as the fallback for fully-compliant browsers:

/* Correct order */
-webkit-transform: rotate(45deg);
-ms-transform: rotate(45deg);
transform: rotate(45deg); /* Standard comes last */

Don't Over-Prefix

Not every property needs prefixes. Modern properties like Grid Layout work without prefixes in all modern browsers. Our tool only adds prefixes where actually needed.

Integrate Into Build Process

For production workflows, integrate autoprefixing into your build pipeline using PostCSS Autoprefixer. This tool is perfect for quick checks, prototyping, and learning.

Browser Support Targeting

Modern Browsers Only

If supporting only modern browsers (Chrome 80+, Firefox 75+, Safari 13+):

• Fewer prefixes needed
• Smaller CSS files
• Faster page loads

Legacy Browser Support

If supporting IE11 and older browsers:

• More prefixes required
• -ms- prefixes essential
• Larger CSS files

Mobile-First

Mobile browsers typically need:

• -webkit- for iOS Safari
• -webkit- for Android WebView
• Standard properties for Chrome Mobile

Common Autoprefixing Scenarios

Flexbox Layout

Flexbox requires extensive prefixing for IE10-11:

/* Input */
.container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* Output */
.container {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-pack: justify;
  -ms-flex-pack: justify;
  justify-content: space-between;
  -webkit-box-align: center;
  -ms-flex-align: center;
  align-items: center;
}

CSS Animations

Animations need WebKit prefixes for older Safari:

/* Input */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* Output includes */
@-webkit-keyframes fadeIn { ... }
@keyframes fadeIn { ... }

CSS Filters

Filter effects require WebKit prefixes:

/* Input */
.blurred {
  filter: blur(5px);
  backdrop-filter: blur(10px);
}

/* Output */
.blurred {
  -webkit-filter: blur(5px);
  filter: blur(5px);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
}

Frequently Asked Questions

Do I need vendor prefixes in 2024+?

Some properties still benefit from prefixes for maximum compatibility, especially -webkit- for Safari and iOS. The need decreases yearly as browsers standardize.

Will prefixes hurt modern browsers?

No. Modern browsers simply ignore prefixes they don't need. The standard property (last in the list) takes precedence.

Should I remove old prefixes?

Yes, periodically. As browser support evolves, some prefixes become unnecessary. Tools like Autoprefixer use "browserslist" to add only needed prefixes.

Does this work with CSS-in-JS?

This tool processes raw CSS. For CSS-in-JS (styled-components, Emotion), use the library's built-in autoprefixing or a PostCSS plugin.

What about CSS Grid?

CSS Grid has excellent support without prefixes in all modern browsers. Only IE11 needs -ms- prefixes for the older Grid syntax.

Is the prefixed CSS larger?

Yes, typically 20-50% larger. For production, use minification after autoprefixing. Consider modern-only builds for users with current browsers.

Integration with Development Workflows

PostCSS Autoprefixer

For build pipelines, use PostCSS Autoprefixer:

npm install autoprefixer postcss

Configure in postcss.config.js:

module.exports = {
  plugins: [
    require('autoprefixer')
  ]
}

Browserslist Configuration

Control which browsers to support via .browserslistrc:

last 2 versions
> 1%
not dead

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Paste your CSS above to automatically add vendor prefixes. Ensure maximum browser compatibility with minimal effort.