javascript - Why does navigator.appCodeName return Mozilla?

Question

The following JavaScript code returns "Mozilla" on all browsers. Why?

 <script type="text/javascript">
 document.write("Browser CodeName: " + navigator.appCodeName);
 </script>

Answer 1

Short answer: Because people thought that user agent detection (instead of feature (AKA object) detection) was a good idea, so browser vendors started lying in order to compensate.

Long answer: History of the browser user-agent string