FaceTime supports iOS URL schemes, enabling users to initiate a call by clicking on a hyperlink. iPhone 3GS users can see and click the links but they don't work, not even for audio-only calls. Yet.

Reader Felipe Baez discovered facetime:// URL scheme support while examining how FaceTime works. iOS began supporting URL schemes a couple years ago; the feature enables webpage links or apps to launch other apps on the phone.

Introducing URL schemes

Apple supports a variety of URL schemes for launching bundled iOS apps from a URL (or programmatically within an app). For example, tel://8008675309 prompts the user to dial that number. It also works with alpha characters, so tel://888facetime correctly translates the letters into the corresponding numbers to dial.

Additionally, mailto://[email protected] would launch Mail app with that addressee, and sms:// (followed by a mobile number or short code) launches Messages with a text addressed and ready to enter.

Apple also opened the URL scheme concept up to third party developers so they can register their own URL scheme. While http://facebook.com/ always launches the web app version of Facebook using Safari, links beginning with fb:/ will launch the Facebook app instead (as long as it's installed).

Linking to FaceTime

It's therefore not surprising that Apple's FaceTime has its own URL scheme that allows other apps (or hyperlinks on a web page) to initiate a video chat. What is interesting, but not surprising, is that the URL scheme isn't enabled on anything other than iPhone 4.

Oddly however, on other iPhone models running iOS 4, FaceTime URLs are recognized as a valid URL scheme. So rather than not being clickable or resulting in an error message that the URL is "invalid" (as an unrecognized URL scheme does), iPhone 3GS users who click on a facetime:// URL get a strangely blank screen (below).

This could be a simple mistake by Apple, or could be evidence that partial support for FaceTime calls was pulled late in the release. Earlier iPhones don't have the processing muscle to handle a video call, but they should be able to handle an audio-only call. Being able to place free, audio-only iChat conversations from any iPhone running iOS would certainly be an attractive feature to users, particularly international callers.