# @csstools/postcss-alpha-function > Use the alpha() function in CSS Latest version **2.0.13** (published 2026-09-13) · MIT-0 license · 0 weekly downloads ## Install ```sh npm install @csstools/postcss-alpha-function pnpm add @csstools/postcss-alpha-function yarn add @csstools/postcss-alpha-function bun add @csstools/postcss-alpha-function ``` ## Health **Score 60/100 (C)** — status: active. Positive: esm support; no vulnerabilities; recently updated; high maintenance score. Warnings: low downloads; no types. ## Facts | | | |---|---| | Version | 2.0.13 | | Published | 2026-09-13 | | First published | 2025-08-22 | | Weekly downloads | 0 | | License | MIT-0 | | TypeScript types | none | | Module format | ESM | | Node | >=20.19.0 | | Dependencies | 5 | | Unpacked size | 9.8 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 1053 | | Maintainers | jonathantneal, alaguna, romainmenke | | Keywords | alpha, color, css, design, postcss, postcss-plugin | ## Links - npm: https://www.npmjs.com/package/@csstools/postcss-alpha-function - Repository: https://github.com/csstools/postcss-plugins - Homepage: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-alpha-function#readme - Issues: https://github.com/csstools/postcss-plugins/issues - Funding: https://github.com/sponsors/csstools - npm.io page: https://npm.io/package/@csstools/postcss-alpha-function ## Dependencies (5) - [@csstools/utilities](https://npm.io/package/@csstools/utilities.md) ^3.0.0 - [@csstools/css-tokenizer](https://npm.io/package/@csstools/css-tokenizer.md) ^4.0.0 - [@csstools/css-color-parser](https://npm.io/package/@csstools/css-color-parser.md) ^4.2.3 - [@csstools/css-parser-algorithms](https://npm.io/package/@csstools/css-parser-algorithms.md) ^4.0.0 - [@csstools/postcss-progressive-custom-properties](https://npm.io/package/@csstools/postcss-progressive-custom-properties.md) ^5.1.3 ## Alternatives - [style-dictionary](https://npm.io/package/style-dictionary.md) — 2.0M weekly downloads - [postcss-merge-idents](https://npm.io/package/postcss-merge-idents.md) — 1.7M weekly downloads - [@fontsource/noto-sans](https://npm.io/package/@fontsource/noto-sans.md) — 93.0K weekly downloads - [uglifycss](https://npm.io/package/uglifycss.md) — 71.6K weekly downloads - [mat4-interpolate](https://npm.io/package/mat4-interpolate.md) — 23.3K weekly downloads ## Recent versions - 2.0.13 (latest) — 2026-09-13 - 2.0.12 — 2026-09-06 - 2.0.11 — 2026-08-31 - 2.0.10 — 2026-08-25 - 2.0.9 — 2026-08-15 - 2.0.8 — 2026-07-22 - 2.0.7 — 2026-06-28 - 2.0.6 — 2026-06-14 - 2.0.5 — 2026-05-13 - 2.0.4 — 2026-04-12 - 2.0.3 — 2026-02-21 - 2.0.2 — 2026-01-25 - 2.0.1 — 2026-01-15 - 2.0.0 — 2026-01-14 - 1.0.1 — 2025-09-21 - … 1 more at https://npm.io/package/@csstools/postcss-alpha-function/versions ## README # PostCSS Alpha Function [PostCSS Logo][PostCSS] `npm install @csstools/postcss-alpha-function --save-dev` [PostCSS Alpha Function] lets you use the `alpha` function in CSS, following the [CSS Color] specification. ```css .color { color: alpha(from #dddd / calc(alpha / 2)); } :root { --a-color: alpha(from rgb(2 1 0 / var(--a)) / calc(alpha / 2)); } /* becomes */ .color { color: rgb(from #dddd r g b / calc(alpha / 2)); } :root { --a-color: rgb(from rgb(2 1 0 / var(--a)) r g b / calc(alpha / 2)); } ``` ## Usage Add [PostCSS Alpha Function] to your project: ```bash npm install postcss @csstools/postcss-alpha-function --save-dev ``` Use it as a [PostCSS] plugin: ```js const postcss = require('postcss'); const postcssAlphaFunction = require('@csstools/postcss-alpha-function'); postcss([ postcssAlphaFunction(/* pluginOptions */) ]).process(YOUR_CSS /*, processOptions */); ``` ## Options ### preserve The `preserve` option determines whether the original notation is preserved. By default, it is not preserved. ```js postcssAlphaFunction({ preserve: true }) ``` ```css .color { color: alpha(from #dddd / calc(alpha / 2)); } :root { --a-color: alpha(from rgb(2 1 0 / var(--a)) / calc(alpha / 2)); } /* becomes */ .color { color: rgb(from #dddd r g b / calc(alpha / 2)); color: alpha(from #dddd / calc(alpha / 2)); } :root { --a-color: rgb(from rgb(2 1 0 / var(--a)) r g b / calc(alpha / 2)); } @supports (color: alpha(from red / 1)) and (color: rgb(0 0 0 / 0)) { :root { --a-color: alpha(from rgb(2 1 0 / var(--a)) / calc(alpha / 2)); } } ``` ### enableProgressiveCustomProperties The `enableProgressiveCustomProperties` option determines whether the original notation is wrapped with `@supports` when used in Custom Properties. By default, it is enabled. > [!NOTE] > We only recommend disabling this when you set `preserve` to `false` or if you bring your own fix for Custom Properties. > See what the plugin does in its [README](https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-progressive-custom-properties#readme). ```js postcssAlphaFunction({ enableProgressiveCustomProperties: false }) ``` ```css .color { color: alpha(from #dddd / calc(alpha / 2)); } :root { --a-color: alpha(from rgb(2 1 0 / var(--a)) / calc(alpha / 2)); } /* becomes */ .color { color: rgb(from #dddd r g b / calc(alpha / 2)); color: alpha(from #dddd / calc(alpha / 2)); } :root { --a-color: rgb(from rgb(2 1 0 / var(--a)) r g b / calc(alpha / 2)); --a-color: alpha(from rgb(2 1 0 / var(--a)) / calc(alpha / 2)); } ``` _Custom properties do not fallback to the previous declaration_ ## Copyright : color conversions This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/tree/main/css-color-4. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang). [cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test [css-url]: https://cssdb.org/#alpha-function [discord]: https://discord.gg/bUadyRwkJS [npm-url]: https://www.npmjs.com/package/@csstools/postcss-alpha-function [PostCSS]: https://github.com/postcss/postcss [PostCSS Alpha Function]: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-alpha-function [CSS Color]: https://drafts.csswg.org/css-color-5/#relative-alpha --- _Source: https://npm.io/package/@csstools/postcss-alpha-function · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._