css-inline: High-Performance CSS Inliner for HTML

css-inline is a high-performance Python library (version 0.20.2) for inlining CSS into HTML 'style' attributes. Built on components from Mozilla's Servo project, it is significantly faster than other alternatives and is primarily designed for use cases such as preparing HTML emails or embedding HTML into third-party web pages where inline styles are a requirement. It's actively maintained with regular releases.