PostCSS Prefix Wrap

A PostCSS (postcss.org) plugin which prepends a selector to CSS styles to constrain their effect on parent elements in a page.

Supports	Versions
Bun (bun.sh)	latest
Deno (deno.com)	v2
NodeJS (nodejs.org)	v22, v24
PostCSS (postcss.org)	v7, v8

⚠️ PostCSS v7 support is no longer validated in automated test cases, and will be removed entirely in a future release.

• How to use this plugin?
• What options does it have?
• What problems can it solve?
• How to contribute?
• Is this project secure?
• License

How to use this plugin?

⚠️ These instructions are only for this plugin. See the PostCSS (postcss.org) website for framework information.

Install

Package Manager or Runtime	Command
Bun (bun.sh)	bun add postcss-prefixwrap --dev --exact
Deno (deno.com)	deno add npm:postcss-prefixwrap --dev
NPM (npmjs.com)	npm install postcss-prefixwrap --save-dev --save-exact
PNPM (pnpm.io)	pnpm add postcss-prefixwrap --save-dev --save-exact
Yarn (yarnpkg.com)	yarn add postcss-prefixwrap --dev --exact

Configure

Add to your PostCSS (postcss.org) configuration.

const PostCSS = require("gulp-postcss");
const PrefixWrap = require("postcss-prefixwrap");

PostCSS([PrefixWrap(".my-custom-wrap")]);

Container

Add the container to your markup.

<div class="my-custom-wrap"><!-- Your existing markup. --></div>

View

View your CSS, now prefix-wrapped.

Before

p {
    color: red;
}

body {
    font-size: 16px;
}

After

.my-custom-wrap p {
    color: red;
}

.my-custom-wrap {
    font-size: 16px;
}

What options does it have?

PrefixWrap(".my-custom-wrap", {
    // You may want to exclude some selectors from being prefixed, this is
    // enabled using the `ignoredSelectors` option.
    ignoredSelectors: [":root", "#my-id", /^\.some-(.+)$/],

    // You may want root tags, like `body` and `html` to be converted to
    // classes, then prefixed, this is enabled using the `prefixRootTags`
    // option.
    // With this option, a selector like `html` will be converted to
    // `.my-container .html`, rather than the default `.my-container`.
    prefixRootTags: true,

    // In certain scenarios, you may only want `PrefixWrap()` to wrap certain
    // CSS files. This is done using the `whitelist` option.
    // ⚠️ **Please note** that each item in the `whitelist` is parsed as a
    // regular expression. This will impact how file paths are matched when you
    // need to support both Windows and Unix like operating systems which use
    // different path separators.
    whitelist: ["editor.css"],

    // In certain scenarios, you may want `PrefixWrap()` to exclude certain CSS
    // files. This is done using the `blacklist` option.
    // ⚠️ **Please note** that each item in the `blacklist` is parsed as a
    // regular expression. This will impact how file paths are matched when you
    // need to support both Windows and Unix like operating systems which use
    // different path separators.
    // If `whitelist` option is also included, `blacklist` will be ignored.
    blacklist: ["colours.css"],

    // When writing nested css rules, and using a plugin like `postcss-nested`
    // to compile them, you will want to ensure that the nested selectors are
    // not prefixed. This is done by defining the `nested` property and setting
    // the value to the selector prefix being used to represent nesting, this is
    // most likely going to be `"&"`.
    nested: "&",

    // A custom transform can be provided that allows your code to determined
    // how the prefix will be applied to each selector.
    prefixTransform: (selector: string, prefixSelector: string) => {
        const insertIndex = selector.indexOf(".m_");

        // If `.m_` not found, just return selector unchanged.
        if (insertIndex === -1) {
            return selector;
        }

        // Place the prefix (with a space) before the `.m_`.
        return `${selector.slice(0, insertIndex)}${prefixSelector} ${selector.slice(insertIndex)}`;
    },
});

What problems can it solve?

PostCSS Prefix Wrap can be used to solve multiple different problems. The following articles give some concrete examples:

• Embedding Content Within an Existing Site With PostCSS Prefix Wrap (tedman.dev)
• Maintainable Legacy CSS With PostCSS Prefix Wrap (tedman.dev)

How to contribute?

Read our Contributing Guide to learn more about how to contribute to this project.

Is this project secure?

Read our Security Guide to learn how security is considered during the development and operation of this plugin.

License

The MIT License is used by this project.