* In addition to the userstyles.org site, styles with customizable parameters can also be installed from .user.css or .user.styl URLs (see [Usercss format wiki](https://github.com/openstyles/stylus/wiki/Usercss)).
* Site styles can be discovered and previewed in the popup using inline search with screenshot thumbnails.
* A backup feature which is compatible with other userstyles managers.
* Configurable automatic update function for installed styles.
* Customizable UI, optional layouts, and tweaks.
* Two different optional code validators with user-configurable rules: CSSLint and Stylelint.
* Both validators use Web Worker API to run in a separate background thread inside the editor tab without blocking your interaction with the code.
* CSSLint is heavily modified compared to the effectively frozen original one and supports various CSS3 features as well as CSS4 Color and CSS Grid syntax.
3. [Opera add-ons](https://addons.opera.com/extensions/details/stylus/) (see [wiki](https://github.com/openstyles/stylus/wiki/Opera,-Outdated-Stylus) for more recent version)
The licenses of [external libraries](./vendor) used in this project or [modified versions of external libraries](./vendor-overwrites) can be found in their respective directory.