I could see where the tel protocol could potentially be used to initiate a call on your desktop providing you had an installed softphone with a SIP account that had POTS termination.
]]>But yeah in Chrome tel: and sms: links don’t seem to do anything at all (I would expect at least an error dialog) but I suspect Skype would register at least one of those, and Google Voice would be a perfect candidate to register handlers for both.
]]>Ugh. That deprives desktop browsers, desktop browser add-ons, and other unknown browsers of the semantic information that they could use to do something useful with those links. Gmail supports sending text messages, for example – so a desktop browser add-on that does something clever with sms: protocol links to open up an appropriate gmail chat window would be perfectly possible… unless the web page decided not to bother sending sms: links to desktop browsers. Pretty sure there are web telephony apps for desktop computers that support making voice calls to phone numbers, as well.
In an ideal world (in my opinion) browser makers would be responsible for doing something sensible with links that they can’t resolve due to unsupported protocols – for example, it’d make sense to stylistically grey them out, add a tooltip indicating the functionality is unavailable, and offer a CSS pseudoclass and something in javascript to enable web authors to detect the situation and react accordingly.
I don’t know what to do in a world where browsers are unintelligent about invalid protocols, but I hate the idea of penalizing (future?) browsers and/or add-ons that ARE smart in order to protect current browsers that aren’t.
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