History of the browser user-agent string (2008)

It gets one better... And Chrome was good, and MSIE wasn't, so webmasters served bad pages to MSIE. Microsoft was not happy. So they created Edge. Edge was good, but Microsoft feared webmasters would treat it like MSIE. So Microsoft Edge pretended to be Chrome to get the good pages. Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36 Edge/12.0

...and everyone pretended to be everyone else, and confusion abounded. And then JavaScript driven feature detection came to be, and everyone thought it was a good idea. And the people wrung their hands and wept

And now we have Chromium-based Opera which can't call itself Opera and has to use "OPR/16" instead, and pretends to be Chrome, which pretends to be Safari, which pretends to be KHTML, which pretends to be Gecko, which pretends to be Netscape. On a related note W3C+Mozilla are trying to document use-cases for UA sniffing: https://etherpad.mozilla.org/uadetection-usecases

The story needs to continue with Microsoft releasing Edge and adding the "Edge" identifier to the user agent string, then in Chromium Edge, changing the identifier to "Edg" because they need to ensure servers do not confuse the new Edge and the old Edge.