Good Addon. Works!
For Europe (Germany) you should set the Number Rules in Settings. I did set:
0)xx xxxxxx
0)xxx xxxxxx
0)xxxx xxxxxx
0)xxxx xxxxxxx
0049xxxxxxxxxx
0049xxxxxxxxxxx
(xxx)xxx-xx-xx
xxx / xx xxx xxx
xxx / xxxx xxxx
xxx / xxx xxx xxx
xxx xx xxx xxx
xxx xxx xxx xxx
xxx xxxx xxxx
xxx xxxxxx
xxx xxxxxxx
xxx xxxxxxxx
xxx xxxxxxxxx

This needs to be completed to work on all numbers. I just started.

To the developer: Good would be someting like a placeholder* like xxx x* to get all Numbers with no matter how many digits a number is long.

Tanks for providing this Addon!

It generally works for more than half the numbers on German websites, after setting Auto Country Prefix to +49. This needs more work for phone numbers with German style formatting. Here some examples which fail to dial the correct numbers:

+49 (0) 69 209 777 777 MeloSIP should drop the (0) in brackets.

08161/ 600 - 288 MeloSIP only dials +498161600, while dropping the 288

German websites use brackets or a slash to separate area codes and lots of spaces and dashes to make the numbers more readable. There are no strict rules for this, thus MeloSIP needs to interpret it as best as it can.

Some major sites do not show any clickable phone numbers, like the national phone directory dastelefonbuch.de

Here MeloSIP needs to add a feature to select and right-click for a ClickToDial context menu item.

I'm using it with the SIP client Bria 5.

I installed the Firefox radon MeloSIP and when I click a phone number it asks if I want to open it with Skype Business. I don’t use it. It does give the option to browse for different apps to associate the Windows protocol, but I’ve no idea what I', suppose to browse to. How do you set up this thing up? I’ve no clue what an API key or other stuff means in the settings. I just want to be able to click phone numbers on the screen and dial with my connected POTS modem. Why no help files, install setup videos or information? Still, support was kind enough to contact me about it and tried to help. Here's part of MeloSIP supports email back to me...

You would require a SIP extension to initiate the calls.
Click2Call >> sennt by API to MeloTel...
MeloTel initiates call to your Ooma number...
You answer the call and it calls the number you clicked...
It would display whatever caller ID you require.
It seems unfortunately this is the only solution we could offer at this time.

4-STARS for great support!

This makes every number that is 7 digits a clickable phone number. There should be a setting added to set a range, like 10 number or 8 number minimum to show as a clickable number.