Windi CSS is an open-source CSS framework heavily inspired by the popular Tailwind CSS CSS framework. Just like Tailwind CSS, Windi CSS uses a utility based approach to styling in which the framework provides a large collection of atomic classes which often correlate to its own CSS property - for example p-2 for adding padding: 0.5 rem. Windi CSS was created as an alternative to Tailwind CSS with more focus on performance as well as minimising the amount of CSS sent to the client. It does this by statically analysing the code base in which it is used in order to determine which CSS classes are used, and therefor should be shipped to the client.
When Windi CSS was first introduced in 2020, it solved a lot of Tailwind's issues related to performance and bundle size, making it a viable alternative to the popular framework. However, Tailwind CSS eventually caught up with many of the previous shortfalls of the framework, notably through the introduction of their Just-in-Time (JIT) engine which analyses class usage in real time - a feature which was likely inspired by competitor frameworks such as Windi CSS.
Due to limited time and resources, the team behind Windi CSS has decided to sunset the framework, meaning that it will no longer receive new feature updates. The framework's documentation suggests to use other alternatives such as Tailwind CSS or the also popular utility-based framework UnoCSS.