Companies like Facebook and Instagram use these unreadable names for several technical reasons:

The specific properties you noted indicate the element's layout and behavior:

The CSS class .xHD8M4Hz is an typically generated by modern web development frameworks or build tools like Webpack or CSS Modules . Because these names are randomized or hashed during the build process, they do not have a standard "meaning" in web development but instead represent a specific, unique style for a UI component on a particular website.

: Adblockers often rely on known class names (like .ad-sidebar ) to hide content; obfuscating these names makes it more difficult for filters to target them accurately. cursor CSS property - MDN Web Docs