With this tool and a small change to the Firefox Application settings, I can call directly from a web page using my Skype for Business client. Even from my Google contacts.

Numbers have to follow exactly the one single format that is recognized by this Add on, or they won't be linkified. +49 123 456789 is detected, but it's not capable handling numbers with special characters as they are customary in Europe like +49 (0) 123 456789 and +49 123/456789. There's no "phone" or custom protocol to use with.

The former Add on "telify" did all this and worked like a charm. But since Mozilla changed the add on API many many extremely good and helpful add ons are gone without replacement.

Can you add custom regex option for number detect?

It's getting better, but now I cannot save the options when I set them.

Works very well for me with zoiper.
Two things would be greate

if it would possible to mark numbers, right click on them and a option to dial it.
and a version for Thunderbird J

Works well so far. I think the number detection could be made better but a good start.

My only real gripe is to do with integration in Google Contacts. When browsing my contacts there Google "helpfully" encloses any phone numbers in a link to Google Hangouts. If I hover over such a number I see a pop up for this plugin but as soon as I move my mouse to try and click the popup, it disappears.

In an ideal world this popup would work and not disappear. In an even more ideal world the Google Hangouts URL would be completely replaced with the relevant URL handler. In a world so ideal it hurts, right clicking on the link would also present the option (as would right clicking on any selected text that vaguely resembles a number, even if it doesn't match the length rules etc).

(ex Telify user here too)

It works perfectly for me as far as clicking a number and it dialing without any issues. My one problem is it also thinks zip codes, account numbers and misc numbers are phone numbers. It will note a phone listed as (555)555-5555 but won't recognize 555-555-5555. If I increase the "max" number to look for it picks up every account number on the page. So I may end up with 50 clickable "phone" links on a page when there should only be two or three. This has been the best replacement for Telify which is no longer compatible with FF I have been able to find. Just a little more tweaking and it will be perfect.