Google announced that Chrome will phase out supporting user-agent strings and switch to a new API, Client Hints, “to give users more control over the information they share with the site.” In reality, Google is one of the few large companies that uses User-Agent to restrict other browsers from using its services, and many sites are optimized for Chrome’s high market share.
This situation has prompted other browsers to fake User-Agent to impersonate Chrome. The use of user-agent strings dates back to the Mosaic browser of the early 1990s.
When a browser visits a web site, it sends a string containing the browser’s name and version number, and Netscape then adopts a user agent string and adds additional information such as the operating system and language. Web sites avoid using features that are not supported by a particular browser version based on user agent string information.
Chrome will phase out support for User-Agent starting with v81 and completely stop supporting v85. It is not known whether other browsers will take similar action.