refreshcss 0.6.0
Removes unused classes, ids, and element selectors from CSS.
License: MIT
Requires Python: >=3.10
Keywords: django, python, css, html

# RefreshCSS 🫧

[![All Contributors](https://img.shields.io/github/all-contributors/adamghill/refreshcss?color=ee8449&style=flat-square)](#contributors)

`RefreshCSS` is a Python library that removes unused classes, ids, and element selectors from CSS.

> Make your CSS so fresh, so clean.

## 🔧 Installation

### To use the `refreshcss` library or use the `django-compressor` integration

`uv add refreshcss`

### To run `refreshcss` on the command-line

`uvx refreshcss[cli]`

## ⭐️ Features

- Pure Python (no extra NodeJS build process needed)
- Fast and spec-compliant CSS and HTML parsing
- Filters out unused classes, ids, and elements from CSS based on HTML templates
- Supports modern CSS syntax, including nested rules, container queries, and media queries
- Handles Django/Jinja-style HTML templates with context-aware extraction
- Integrates with `django-compressor` to clean CSS during the `compress` command
- Command-line interface for use in CI/CD pipelines

### ⌨️ Command-line interface

`uvx refreshcss[cli]`

```sh
Usage: refreshcss [OPTIONS] CSS HTML...

  Remove classes, ids, and element selectors not used in HTML from CSS.

Options:
  -o, --output FILENAME  Write to file instead of stdout.
  -R, -r, --recursive    Recursively search subdirectories listed.
  --encoding TEXT        Character encoding to use when reading files. If not
                         specified, the encoding will be guessed.
  --version              Show the version and exit.
  --help                 Show this message and exit.
```

### 🗜️ Integrate with django-compressor

Add `"refreshcss.filters.RefreshCSSFilter"` to `COMPRESS_FILTERS` in the Django settings file.

```python
COMPRESS_FILTERS = {
    "css": [
        "refreshcss.filters.RefreshCSSFilter",
        ...
    ],
    "js": [...],
}
```

### ⚙️ Library

```python
from refreshcss import RefreshCSS, PathSite

def clean_css(css_path: Path):
    # Parse the HTML files
    site = PathSite(paths=["templates"], recursive=True)
    site.parse()

    # Get clean CSS based on the parsed HTML
    css_text = css_path.read_text()
    cleaned_css = RefreshCSS(site).clean(css_text)

    return cleaned_css
```

## 🤓 How does it work?

1. Catalogue classes, ids, and elements that are currently being used in found HTML templates
1. Catalogue classes, ids, elements, and at-rules in a particular CSS stylesheet
1. Return a new CSS stylesheet that only contains rules that are actively being used by the HTML

## 🧐 Why?

I wanted to have a filter for `django-compressor` that would purge unused CSS as part of the `compress` step when deploying for [`coltrane`](https://coltrane.readthedocs.io) apps. After dealing with a manual process and attempting to integrate https://purgecss.com and https://github.com/uncss/uncss I thought "this couldn't be that hard to do in Python".

Which is always the thought at the beginning of every side project... 😅

## 🙋 FAQ

### Will this work with SPAs?

Probably not. `RefreshCSS` only inspects HTML templates, so if CSS classes are being changed client-side then `refreshcss` will not know about it.

### Does this work by crawling a website URL?

Currently no, although that is a possibility in the future. PRs appreciated. 😉

### Does this support HTML written in the Django Template Language?

Yes! That was a primary reason I built my own solution. 😅 Jinja might also be possible to support with some small tweaks, although it is currently untested.

### Is this what people mean when they say "treeshaking"?

Maybe. 🤷

### I found a bug!

Thanks for trying `RefreshCSS` out! Please make a PR (pull request) with a small test that replicates the bug or, if that is not possible, create a [new discussion](https://github.com/adamghill/refreshcss/discussions/new?category=ideas).

## 🤘 Related libraries

### Node

- [uncss](https://github.com/uncss/uncss)
- [PurgeCSS](https://purgecss.com/)

### Python

- [treeshake](https://pypi.org/project/treeshake/): I unfortunately could not get this to work on my local environment.
- [cssutils](https://pypi.org/project/cssutils/): This unfortunately seemed to choke on more modern CSS when I tested on Bulma 1.0.
- [css-optomizer](https://github.com/hamzaehsan97/CSS-optomizer)

## 🙏 Thanks

- [Django](https://www.djangoproject.com)
- [django-compressor](https://django-compressor.readthedocs.io/)
- [CSS standards](https://www.w3.org/Style/CSS/)

## ❤️ Support

This project is supported by GitHub [Sponsors](https://github.com/sponsors/adamghill) and [Digital Ocean](https://m.do.co/c/617d629f56c0).

<p>
  <a href="https://m.do.co/c/617d629f56c0">
    <img src="https://opensource.nyc3.cdn.digitaloceanspaces.com/attribution/assets/SVG/DO_Logo_horizontal_blue.svg" width="201px">
  </a>
</p>

## 🥳 Contributors

<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
<!-- prettier-ignore-start -->
<!-- markdownlint-disable -->
<table>
  <tbody>
    <tr>
      <td align="center" valign="top" width="14.28%"><a href="https://git.boelz.eu/tmb/"><img src="https://avatars.githubusercontent.com/u/641522?v=4?s=100" width="100px;" alt="Tobias Bölz"/><br /><sub><b>Tobias Bölz</b></sub></a><br /><a href="#code-tobiasmboelz" title="Code">💻</a> <a href="#doc-tobiasmboelz" title="Documentation">📖</a> <a href="#test-tobiasmboelz" title="Tests">⚠️</a></td>
    </tr>
  </tbody>
</table>

<!-- markdownlint-restore -->
<!-- prettier-ignore-end -->

<!-- ALL-CONTRIBUTORS-LIST:END -->