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One (of many) super outcomes of the HTML5 evolution is that browser vendors are striving towards interoperability – even Microsoft is talking of “same markup”.
The W3C defines them as
full-fledged client-side applications that are authored using technologies such as HTML and then packaged for distribution. Examples range from simple clocks, stock tickers, news casters, games and weather forecasters, to complex applications that pull data from multiple sources to be “mashed-up” and presented to a user in some interesting and useful way.
Opera (disclosure: my employer) uses the W3C standard for its packaging format – so the assets are bagged up in a zip file, which is renamed .wgt The configuration information is an XML file that specifies things like required features (eg, camera access), default size of the Widget (full-screen, minimised etc) and its network access permissions. (Learn more or download some widgets and have a play).
W3C Widgets work in Opera browsers (and we re-use the format for Opera Extensions), Apache Wookie, Nokia Series 40 phones [PDF], some Vodafone phones, Windows Mobile 6.5 (although in Win Phone 7 you have to use Silverlight, yay Same markup!) and other places, such as forthcoming interactive classroom whiteboards and TVs.
Chrome has a widget format called .crx that is so similar to W3C Widgets that Scott Wilson wrote a Chrome apps to W3C Widget converter, saying
I was intrigued to find out what sort of formats the Chrome Web Store was using for its “installed web applications”, and discovered somewhat to my surprise it uses yet another packaging and manifest format! This is in addition to the two manifest formats Google already uses (for Gadgets/OpenSocial/Wave and Google App Market).
The format uses the file extension “.crx” and consists of a 7-Zip archive and a manifest file in JSON. The actual contents however are almost identical to W3C Widgets, and so I created a proof-of-concept set of conversion code.
My question to chums in Chrome and Mozilla (which has its own Mozilla Install Manifest format): what’s missing from the standard W3C Widgets specification that you need? Wouldn’t it be better for us all to collaborate on one interoperable specification, as we’re doing so successfully with HTML5?
My chum Marcos Caceres is the editor of the Widgets spec and would doubtless leuurve your feedback.
Update 24 July 2012. I never got an answer from Chrome, but they have announced their own non-standards-based proprietary Packaged Apps format. Hurray for interoperability.