TomTom website opens client software

Question

I recently received an e-mail about a TomTom map update and clicking through the website appeared to be a 'special link' which opened the TomTom client software when clicking. Because I'm on a different machine I obviously can't test it, but the anchor link looks like this:

<a href="tomtomhome:contentitems-of-type:map">Start TomTom HOME</a>

This doesn't look like a normal link - so how does it work? What do the colons (:) mean? Does it really allow client software to be opened via a website click?

Answer 1

The part before the double colon is the protocol to handle the url (so here tomtomhome). They must have registered this custom protocol when you installed the client software.

More info about registering custom url protocols: How do I register a custom URL protocol in Windows?