I've used the user agent at work before. We were building something similar to Googles app store for a telecom, and we used it to know which file to serve to th

I've used the user agent at work before. We were building something similar to Googles app store for a telecom, and we used it to know which file to serve to the user when they clicked download. Since we supported all kinds of phones (including old ones that used Java files for games), we couldn't just serve an apk file.