Consti

Not quite correct. For html, that is to signal standard compliance, you can leave it away and the browser will still handle it. For the bash one, all (most) shell scripts use .sh, so you need to give a shebang to tell the loader which executable (sh, bash, zsh, csh, …) to use

Also on Linux xdg does take file extensions into account, just executables do not

It’sintended to be used when the cookies are actually required for the app to work. For example, to preserve your login, you need a cookie, no way around. Unfortunately, as mentioned by others, it’s often abused

It does look that way, but a diagram is pretty useless if the only way to interpet it is “guess”

And there are more lines, it would be interesting to know what years the other lines are, to maybe see a trend

You removed the legend, what do the colours mean?