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https://github.com/jake-low/postcss-minify

PostCSS plugin to remove comments and unnecessary whitespace from CSS files
https://github.com/jake-low/postcss-minify

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PostCSS plugin to remove comments and unnecessary whitespace from CSS files

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# postcss-minify



[PostCSS] plugin to remove comments and unnecessary whitespace from CSS files.



Input:



```css

body {

  /* make it big and red */

  font-size: large;

  color: red;

}

```



Output:



```css

body{font-size:large;color:red}

```



## Usage



Install with `npm install postcss-minify` and use [as you would any other PostCSS plugin](https://github.com/postcss/postcss#usage).



## Why



postcss-minify offers a minimalist alternative to sophisticated CSS optimizers

like [cssnano], [csso] and [clean-css]. These projects analyze your CSS and

find ways to rewrite it in order to reduce the total character count. For

example, they can merge rules with the same selector, rewrite longhand

properties using shorthand equivalents, and precompute `calc()` expressions

that evaluate to constants.



These clever techniques can help you squeeze a few more bytes out of your CSS,

but they come with a lot of complexity. You may encounter bugs in these tools

that make unsafe changes to your CSS, or find that changes which are

theoretically safe behave surprisingly in older browsers. For some projects,

the bytes saved may not be worth the risk incurred by this added complexity.



In contrast to these powerful optimizers, postcss-minify _only_ makes trivial

modifications to its input: it removes unnecessary whitespace and discards

comments. This means it can be very simple (just 50 lines of code) and carry

less risk of modifying your CSS in a way that breaks your website.



It turns out that in many situations, postcss-minify's naive approach to

minification performs almost exactly as well as much more sophisticated

techniques. Here's a quick experiment I ran where I minified [bootstrap.css]

using various CSS optimizers and then compared the pre- and post-gzip size

reductions.



|                                                      | [clean-css] | [cssnano] | [csso]    | postcss-minify |

|------------------------------------------------------|-------------|-----------|-----------|----------------|

| version tested                                       | 5.1.2       | 5.0.0     | 4.2.0     | 1.0.0          |

| lines of code (sloc)                                 | 7,170¹      | 8,159     | 2,534     | 50             |

| minified size of bootstrap.css 5.0 (195,075 bytes)   | 154,829     | 154,334   | 153,683   | 157,375        |

| ratio to unminified bootstrap.css                    | 0.794       | 0.791     | 0.788     | 0.807          |

| after gzipping minified output                       | 22,850      | 22,934    | 23,009    | 22,893         |

| ratio to gzipped bootstrap.css 5.0 (25,238 bytes)    | 0.905       | 0.909     | 0.912     | 0.907          |



As you can see, postcss-minify does almost as good a job of minifying this

large, real-world CSS file as the more complex tools. And after gzip

compression is applied to the results, the differences become insignificant.

You'd save a mere 43 bytes by using clean-css over postcss-minify,² which even

on a 2G mobile connection represents an increased download time of about 7ms.



Your mileage will vary of course. In certain situations (for example, when

minifying CSS which was generated using Sass `@mixins`), advanced techniques

will be able to substantially reduce the size of your CSS code by merging rules

and deleting duplicate declarations. But in many cases, naive minification will

get you 90% of the compression with 2% of the complexity.



1: clean-css includes its own CSS parser, while the others depend on either

postcss or css-tree. To ensure a fair comparison, I've only included the code

in the lib/optimizer/ directory of clean-css. The total codebase is about

10,125 SLOC.



2: That's about the length of this footnote.



## License



This repository is made available under the MIT license; see the included

LICENSE file for details.



[PostCSS]: https://github.com/postcss/postcss

[cssnano]: http://github.com/cssnano/cssnano

[csso]: http://github.com/css/csso

[clean-css]: https://github.com/jakubpawlowicz/clean-css

[bootstrap.css]: https://getbootstrap.com/docs/5.0/getting-started/download/