@parcel/css
A CSS parser, transformer, and minifier written in Rust.
Features
- Extremely fast – Parsing and minifying large files is completed in milliseconds, often with significantly smaller output than other tools. See benchmarks below.
- Typed property values – many other CSS parsers treat property values as an untyped series of tokens. This means that each transformer that wants to do something with these values must interpret them itself, leading to duplicate work and inconsistencies.
@parcel/css
parses all values using the grammar from the CSS specification, and exposes a specific value type for each property. - Browser-grade parser –
@parcel/css
is built on the cssparser and selectors crates created by Mozilla and used by Firefox and Servo. These provide a solid general purpose CSS-parsing foundation on top of which@parcel/css
implements support for all specific CSS rules and properties. - Minification – One of the main purposes of
@parcel/css
is to minify CSS to make it smaller. This includes many optimizations including:- Combining longhand properties into shorthands where possible.
- Merging adjacent rules with the same selectors or declarations when it is safe to do so.
- Combining CSS transforms into a single matrix or visa versa when smaller.
- Removing vendor prefixes that are not needed, based on the provided browser targets.
- Reducing
calc()
expressions where possible. - Converting colors to shorter hex notation where possible.
- Minifying gradients.
- Normalizing property value order.
- Removing default property sub-values which will be inferred by browsers.
- Many micro-optimizations, e.g. converting to shorter units, removing unnecessary quotation marks, etc.
- Vendor prefixing –
@parcel/css
accepts a list of browser targets, and automatically adds (and removes) vendor prefixes. - Syntax lowering –
@parcel/css
parses modern CSS syntax, and generates more compatible output where needed, based on browser targets.- CSS Level 4 Color syntax
- Space separated components in
rgb
andhsl
functions - Hex with alpha syntax
hwb()
color syntax- Percent syntax for opacity
- Space separated components in
- Double position gradient stops (e.g.
red 40% 80%
) clamp()
function- Alignment shorthands (e.g.
place-items
) - Two-value
overflow
shorthand - Media query range syntax (e.g.
@media (width <= 100px)
or@media (100px < width < 500px)
) - Multi-value
display
property (e.g.inline flex
)
- CSS Level 4 Color syntax
- CSS modules – TODO
Documentation
@parcel/css
can be used from Parcel, as a standalone library from JavaScript or Rust, or wrapped as a plugin within any other tool.
From JavaScript
More docs to come, but here is a simple example:
const css = require;
let = css.;
From Rust
See the Rust API docs on docs.rs.
With Parcel
Add the following to your .parcelrc
:
Benchmarks
$ node bench.js bootstrap-4.css
cssnano: 542.956ms
159636 bytes
esbuild: 17.411ms
160332 bytes
parcel-css: 4.74ms
143985 bytes
$ node bench.js animate.css
cssnano: 283.105ms
71723 bytes
esbuild: 11.858ms
72183 bytes
parcel-css: 1.989ms
23666 bytes
$ node bench.js tailwind.css
cssnano: 2.198s
1925626 bytes
esbuild: 107.668ms
1961642 bytes
parcel-css: 45.701ms
1799209 bytes