postcss-rem-to-viewport

A plugin for PostCSS that generates viewport units from rem units.

If you need to combine this behavior with other unit conversions or custom presets, prefer postcss-rule-unit-converter. Keep this package when you want the legacy rem -> viewport API surface unchanged. For equivalent config examples, see postcss-rule-unit-converter migration guide.

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• Rewrite with typescript and well tested.
• TransformUnit Support vw and others !
• Internally reuses shared utilities from postcss-plugin-shared.

Install

npm i -D postcss-rem-to-viewport
yarn add -D postcss-rem-to-viewport
pnpm i -D postcss-rem-to-viewport

Usage

Use with postcss.config.js

// postcss.config.js
module.exports = {
  plugins: [
    require('postcss-rem-to-viewport')({
      // default: rootValue: 375,
    }),
  ],
}

Options

Type: Object | Null Default:

const defaultOptions = {
  rootValue: 375, // number | (input) => number
  unitPrecision: 16,
  selectorBlackList: [],
  propList: ['font', 'font-size', 'line-height', 'letter-spacing'],
  replace: true,
  mediaQuery: false,
  minRemValue: 0,
  exclude: [/node_modules/i],
  transformUnit: 'vw',
  disabled: false
}

rootValue

Type: number | (input) => number Default: 375

The root element font size. can be 750 or other

100vw = 375px = 23.4375rem

unitPrecision

Type: number Default: 16

The decimal precision px units are allowed to use, floored (rounding down on half).

propList

Type: (string | RegExp)[]

The properties that can change from rem to px.

String entries keep the existing substring-match behavior. String entries starting with ! exclude properties. If a string contains *, it is treated as a glob pattern:

propList: ['*', '!font-size', '!padding*', '!--wot-*-font-size']

selectorBlackList

Type: (string | RegExp)[]

The selectors to ignore and leave as rem.

replace

Type: boolean

replaces rules containing rems instead of adding fallbacks.

mediaQuery

Type: boolean

Allow rem to be converted in media queries.

minRemValue

Type: number

Set the minimum rem value to replace.

exclude

Type: (string | RegExp)[] | ((filePath: string) => boolean)

The file path to ignore and leave as px.

Choosing Between exclude, selectorBlackList, and propList

• exclude: skip the whole file before any declaration is processed
• selectorBlackList: skip matching selectors inside an otherwise processed file
• propList: skip or include specific CSS properties inside matched selectors

Use exclude for file-level boundaries such as node_modules or generated CSS. Use selectorBlackList when a rule or component should be left untouched. Use propList when the file and selector should still be processed, but some properties such as font-size or --wot-*-font-size should be skipped.

transformUnit

Type: string Default: vw

The transform output unit.

disabled

Type: boolean

If disable this plugin.

A message about ignoring properties

Currently, the easiest way to have a single property ignored is to use a capital in the rem unit declaration.

/* `rem` is converted to `px` */
.convert {
  font-size: 1rem;
}

/* `Rem` or `REM` is ignored by `postcss-rem-to-pixel` but still accepted by browsers */
.ignore {
  border: 1Rem solid;
  border-width: 2REM;
}

Thanks to the author of postcss-rem-to-pixel and postcss-pxtorem.