Are you referring to user agents? Serving different code based on user agent is considered bad practice, and would be a maintenance nightmare. Not to mention, s

Are you referring to user agents? Serving different code based on user agent is considered bad practice, and would be a maintenance nightmare. Not to mention, serving different JavaScript would make it more difficult to reason about what is running client-side. Plus, user agents are neither canonical nor necessarily even reliable sources of information about the browser.