What is Silverlight, really?

Microsoft's Silverlight technology, launched at the NAB conference two weeks ago and pitched hard to developers at the Mix '07 conference this week, is being taken as a competitor to Adobe's Flash. Since it is a framework for providing rich applications to the Internet browser, it is indeed that. But though Silverlight and Flash are competing technologies, Microsoft's offering is different from Adobe's in key ways.

More than just a platform

Silverlight is being pushed side-by-side with Microsoft's Live services for developers. Microsoft is opening up APIs (application program interfaces) for its search engine, for Virtual Earth, for its instant messaging service, and for other services, under generous, but not unlimited, licensing terms. These services will allow the creation of interesting online applications that take advantage of existing Microsoft networks and resources. For example, Match.com today demoed a new version of its service that can connect directly to other Match.com subscribers who are MSN Messenger users. Mash-ups are nothing new, of course, but it is important that Microsoft is giving developers access to its computing resources as well as its user base.

Silverlight supports the display of high-definition video files, and importantly, Microsoft will do the heavy lifting of sending them over the Net. Streaming large media files is expensive, but Microsoft will (optionally) host Silverlight media files and applications. This will enable smaller developers to deliver large and high-definition files quickly and reliably, without paying content distribution network fees. Microsoft is promising reliable 700kbps throughput for media files, and free distribution of all content on its network for one year. After that, distribution will continue to be free up to 1 million streamed minutes a month. Fees after that have not been set.

Also, Silverlight applications are delivered to a browser in a text-based markup language called XAML. That's no big deal for Web users once they land on a site. But search engines, like Google, can scan XAML. They can't dive into compiled Flash applications. Flash-heavy sites do often wrap their applications in Web code that search engines can crawl, although it's extra work for developers and designers to do it, and may not yield search results that are as good as they would be if the search engine was indexing the actual application instead of keywords tacked on after the fact. Silverlight applications will be more findable.

One thing Silverlight isn't though, is a competitor to Apollo (hands-on), Adobe's technology that lets developers take their online applications and make them into standalone desktop apps. Apollo developers will be able to take advantage of capabilities that make applications behave properly whether they are online or not. Silverlight does not yet offer those capabilities, although I heard that apps written in Silverlight will be able to modify the "chrome" or basic user interface of a browser while they are running, to further obscure the difference between a browser-based app and traditional software.

But what's in it for me?

Windows users probably won't care whether the rich Web app they are visiting is using Silverlight or Flash. Both technologies require a small plug-in (as of IE7, Flash is no longer bundled with the browser) and once installed, both are invisible until the user hits a page that requires their services.

Web developers will care about which technology they choose, though. Publishers and developers want their apps to run on as many platforms as possible, and while Silverlight apps will run on both major Windows browsers as well as on Safari and Firefox on a Mac, Microsoft does not have a sterling track record in delivering ongoing support for Mac apps and platforms. Nonetheless, the developer community seems to have given Silverlight a thumbs-up, so expect to see interesting new Web apps coming out that use it.

Already, Microsoft has done a good job of lining up top-tier developers. At the launch of the conference, we saw demos from Netflix (video), Major League Baseball (video), and CBS. All showed applications that combined very impressive user interaction, streaming video, and interesting community features. Netflix, for example, lets two users sync their videos so they're both watching the same movie together. MLB lets one person send another a clip of an in-game event, which displays in a picture-in-picture view on their game display.

It looks like Silverlight is not just solid technology, but that Microsoft has also put together an infrastructure of supporting services offered at can't-say-no prices. The Web was hardly hurting for innovation up to now, but Silverlight will likely encourage even more of it.

To download the Silverlight plug-in and check out the Silverlight demos, go to Microsoft's Silverlight site.

Other Silverlight stories worth reading:

• TechCrunch: The Web Just Got Richer
• Scobleizer: Microsoft "rebooted the Web"
• News.com: Microsoft takes Silverlight beyond Windows
• News.com: Ray Ozzie interview
• More Webware stories on Silverlight