posted 3 years ago
It's important to remember that web browsers don't receive "files", they receive data streams. The data stream's "type" should be marked via a Content-Type header.
Content-type refers to a MIME value. MIME, incidentally, stands for Multimedia Internet Mail Extensions, since it was first designed for email with non-text content, then adapted for web use.
When a web client (browser) receives a data stream, it looks up the Content-Type MIME type. There's typically a file or database somewhere it references, either client-specific or sometimes system-wide.
The MIME type lookup typically will return what filename extension(s) that type is associated with. For example, in the global MIME mapping (/etc/mime.types) file on my machine, the type application/gzip assiciates with "gz" and "gzip" file extensions.
In-browser MIME mapping may also specify the default disposition for a data stream - that is, "display in browser" or "save as file".
So the file save options dialog's selection of default file types for a given Content-Type depends on the browser and the browser's preferences possibly augmented by sysytem preferences.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.