@css-inline/css-inline
Advanced tools
High-performance library for inlining CSS into HTML 'style' attributes
css-inline is a high-performance library for inlining CSS into HTML 'style' attributes.
This library is designed for scenarios such as preparing HTML emails or embedding HTML into third-party web pages.
For instance, the library transforms HTML like this:
<html>
<head>
<style>h1 { color:blue; }</style>
</head>
<body>
<h1>Big Text</h1>
</body>
</html>
into:
<html>
<head></head>
<body>
<h1 style="color:blue;">Big Text</h1>
</body>
</html>
style and link tagsstyle and link tagsIf you'd like to try css-inline, you can check the WebAssembly-powered playground to see the results instantly.
Install with npm:
npm i @css-inline/css-inline
import { inline } from "@css-inline/css-inline";
var inlined = inline(
`
<html>
<head>
<style>h1 { color:red }</style>
</head>
<body>
<h1>Test</h1>
</body>
</html>
`,
);
// Do something with the inlined HTML, e.g. send an email
inlineStyleTags. Specifies whether to inline CSS from "style" tags. Default: truekeepStyleTags. Specifies whether to keep "style" tags after inlining. Default: falsekeepLinkTags. Specifies whether to keep "link" tags after inlining. Default: falsebaseUrl. The base URL used to resolve relative URLs. If you'd like to load stylesheets from your filesystem, use the file:// scheme. Default: nullloadRemoteStylesheets. Specifies whether remote stylesheets should be loaded. Default: trueextraCss. Extra CSS to be inlined. Default: nullpreallocateNodeCapacity. Advanced. Preallocates capacity for HTML nodes during parsing. This can improve performance when you have an estimate of the number of nodes in your HTML document. Default: 32You can also skip CSS inlining for an HTML tag by adding the data-css-inline="ignore" attribute to it:
<head>
<style>h1 { color:blue; }</style>
</head>
<body>
<!-- The tag below won't receive additional styles -->
<h1 data-css-inline="ignore">Big Text</h1>
</body>
</html>
The data-css-inline="ignore" attribute also allows you to skip link and style tags:
<head>
<!-- Styles below are ignored -->
<style data-css-inline="ignore">h1 { color:blue; }</style>
</head>
<body>
<h1>Big Text</h1>
</body>
Alternatively, you may keep style from being removed by using the data-css-inline="keep" attribute.
This is useful if you want to keep @media queries for responsive emails in separate style tags:
<head>
<!-- Styles below are not removed -->
<style data-css-inline="keep">h1 { color:blue; }</style>
</head>
<body>
<h1>Big Text</h1>
</body>
Such tags will be kept in the resulting HTML even if the keep_style_tags option is set to false.
css-inline also ships a WebAssembly module built with wasm-bindgen to run in browsers.
<script src="https://unpkg.com/@css-inline/css-inline-wasm"></script>
<script>
// Initialize the WASM module first
cssInline.initWasm(fetch('https://unpkg.com/@css-inline/css-inline-wasm/index_bg.wasm'));
const inlinedHtml = cssInline.inline(`<html>
<head>
<style>h1 { color:blue; }</style>
</head>
<body>
<h1>Big Text</h1>
</body>
</html>`);
document.getElementById('output').src = inlinedHtml
</script>
NOTE: WASM module currently lacks support for fetching stylesheets from network or filesystem.
css-inline is powered by efficient tooling from Mozilla's Servo project and significantly outperforms other JavaScript alternatives in terms of speed.
Most of the time it achieves over a 3x speed advantage compared to the next fastest alternative.
Here is the performance comparison:
| Size | css-inline 0.13.0 | css-inline-wasm 0.13.0 | juice 10.0.0 | inline-css 4.0.2 | |
|---|---|---|---|---|---|
| Basic | 230 B | 15.34 µs | 19.99 µs (1.30x) | 56.70 µs (3.69x) | 67.95 µs (4.42x) |
| Realistic-1 | 8.58 KB | 333.22 µs | 434.59 µs (1.30x) | 1.07 ms (3.23x) | 1.24 ms (3.73x) |
| Realistic-2 | 4.3 KB | 195.80 µs | 261.09 µs (1.33x) | 0.99 ms (5.10x) | 0.76 ms (3.90x) |
The "Basic" case was obtained from benchmarking the example from the Usage section.
The benchmarking code is available in the benches/bench.ts file. The benchmarks were conducted using the stable rustc 1.75.0 on Node.js v21.1.0.
This project is licensed under the terms of the MIT license.
[0.13.0] - 2024-01-19
data-css-inline="keep" attribute to enforce keeping the style tag.attohttpc with reqwest to simplify implementing non-blocking stylesheet resolving in the future release.nth-child. #324FAQs
High-performance library for inlining CSS into HTML 'style' attributes
The npm package @css-inline/css-inline receives a total of 123,276 weekly downloads. As such, @css-inline/css-inline popularity was classified as popular.
We found that @css-inline/css-inline demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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