What is CSS5?

There is no formally defined CSS5. CSS (Cascading Style Sheets) is continuously evolving. After CSS3, the development model shifted to a modular approach where individual features are developed and standardized independently. There isn't a single, monolithic 'CSS4' or 'CSS5' specification. Instead, new CSS features are released as modules, and these modules are often referred to by their level (e.g., CSS Color Module Level 4). Therefore, 'CSS5' is not a recognized or standardized term in web development. If someone uses this term, they likely refer to a collection of newer CSS modules and features that have emerged after CSS3, encompassing ongoing improvements and additions to styling capabilities for web content.