See https://bugzilla.mozilla.org/show_bug.cgi?id=764062#c17 For developers it's quite annoying to work with autofill when they need to input port numbers. Since we have very nice devtools, it's a pity to ruin the experience with this. The best fix may take a while to implement (see bug 764062), and it will still only be able to provide a single result (the most frecent one). Editing the port number may still be quite annoying. For this reason I'm suggesting a quicker fix, that consists into changing the user input when he types ":" on an autofilled entry. Basically "l[ocalhost/]|" becomes "localhost:|" when ":" is pressed. Thus only "l:" is needed to complete to "localhost:". This will also be nice once the underlying bug is fixed to change a suggested port number. This is probably feasible in urlbarbindings.xml and will require a dedicated mochitest-browser test. I'm setting myself as mentor in case someone wants to try implementing this, it's not a good first bug though, it will require some tries and debugging.

let's see how things evolve with new autofill first.