Silverlight vs. Flash

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With the rocket development of Internet, the techniques used for building web pages is improving all the time, which not only brings people more information but new experience of surfing on the Internet. Many techniques have been applied to enrich the web page these years, from totally the plaintext in early 90's, first to web page with pictures and then that with embedded sounds. Later, Sun Microsystems proposed Java Applet, which was popular for not long time until being conquered by Adobe Flash. Now Microsoft proposed Silverlight technology. Some people say that Microsoft made a wrong decision while others claim that Silverlight will kill Flash at last. According to the next step in the value chain, for Flash, it focus on building rich applications with Flex. For Silverlight, Ajax is becoming the way to add more value.

(CC) Image: Ganggang Hu
Made by Ganggang Hu, 2008


When it comes to general technology features, both Flash and Silverlight have the same functions and benefits as follows:

  • Rich 2D animation/graphics with audio and video
  • Choice of standards-based and high-performance languages
  • End-to-end server and application platform
  • Client side playlists for ad-insertion
  • Robust video publishing tools
  • High-performance, multi-core enabled lightweight client
  • Data exchange with web server
  • Easy installation support for platform requirements
  • Tools product line integrity
  • Multiple browsers support such as IE, Firefox, Safari and Opera

On the other hand, both of them have their unique features. For example, Flash has offline document support, rich set of control library and test tools. While Silverlight has hardware-assisted editing and encoding solutions, XML-based presentation for Search Engine Optimization (SEO), and content access protection, Digital Rights Management (DRM).

Below is the table of technology comparison between Flash and Silverlight.

Animation manipulationtime basedframe based
Video codecindustry standard VC-1 codecno industry standard
Audio decoderMP3, WMA, WMVMP3
Binary or text fileXAML text based and XML objectSWF binary shape records
Platform supportWindows, Max OS X, Linux (Moonlight), MobileWindows, Max OS X, Linux, Mobile
Programming toolsVisual Studio, Expression StudioActionScript

Animation manipulation

Flash is frame based, which requires users to compute the duration of an animation. For example, there are 12 frames per second in Flash animation model. If users want an object to move 5 seconds continuously, they need to calculate how many frames 5 seconds will take. Also, the player doesn't maintain any frame rate unless users embed blank audio tracks.

Instead of frame based, Silverlight supports the time based Windows Presentation Foundation (WPF) animation model, which allows users to define the start and end conditions without calculating positions on various frames. Then Silverlight can generate animation process automatically.[1]

Video codec and audio decoder

Flash supports multiple video formats with high quality codec and nice bandwidth usage, such as scalable full screen video up to HD(720p). The price of its media server licensing(unlimited bandwidth) is only one forth of that of Silverlight. Except for its Sorenson’s proprietary H.263 codec, Flash has no industry standard video codec yet. In addition, the audio formats supported by Flash are all proprietary, except for the MP3 and Adaptive Differential Pulse Code Modulation (ADPCM) formats, whose quality of compression are not impressive, and still require licensing fees and third party conversion libraries.

Compare to Flash, Silverlight implements industry standard VC-1 codec for video, and offers support for Windows Media Video (WMV), Windows Media Audio (WMA) and MP3. Microsoft makes available a free Encoder Software Development Kit (SDK) for producing WMA and WMV that allows developers to encode video and audio format for easier integration and cheaper cost.

The table below shows the comparison of video codec between Flash and Silverlight using different computer systems.[2]

 Flash VP6EFlash VP6SFlash H.264-HighSilverlight
PowerMac Dual 2.7 GHz PPC G5, OS 10.4.11, FireFox, Flash Player, SL 1.0.30401.0    
Processor(percentage of 2 processors)72.0%66.3%85.8%108.0%
Drop framesnonoyesyes
Estimated frame ratefullfull5-6 fps1-2 fps
Drop audiononoyesno
HP xw4100, 3.0 GHz P4 with HTT, Windows XP, FireFox Flash Player 9.0.124, SL 1.0.30401.0    
Drop framesyesnoyes-stoppedyes-lost synch
Estimated frame rate2 fpsfullstopped1 frame/3 seconds
Drop audioyesnoyesyes
HP 8710P, 2.2 GHz Core 2 Duao, Vista, IE, Flash, SL 2.0.30226.2    
Drop framesnononono
Estimated frame ratefullfullfullfull
Drop audionononono
Dell Precision 390, 2.9 GHz Core 2 Duo, XP, IE, Flash, SL 2.0.30226.2    
Drop framesnononono
Estimated frame ratefullfullfullfull
Drop audionononono

Binary or text file

Flash stores shapes using binary shape records. In order to write shape definitions, users need to either license a third party Flash file format SDK, or build their own libraries. On the other hand, Silverlight uses text based Extensible Application Markup Language (XAML), which can be output using an XML object. This means that the users do not need to have their own special libraries.

Flash stores fonts glyphs using the same exact shape definitions that are used for any other shape. The player does not understand the True Type Font (TTF) files, which requires users to use the Win32 APIs to figure out the intricacies of fonts in the Flash file format documentation. But in Silverlight, the WPF engine lets users embed True Type Font (TTF) information directly into projects, and download that information using the downloader object without doing any other extra work.

However, with the capability of compiling down into the binary, Flash can actually starts executing before it is fully downloaded, which is one of the serious benefits to using binary SWF (Shockwave Flash) and more satisfying than the pure text files in Silverlight, which brings the runtime from zero to hero before one can do anything. Furthermore, Flash has plenty of functionality encapsulated in the runtime. It has its own just-in-time (JIT) compiler, ActionScript and a healthy set of controls. On the other hand, Silverlight uses JavaScript as the scripting language and depends on the browser for most of the interaction processing.

Platform support

Flash integrates with multiple platforms and languages. It supports Windows, Max OS X, Linux and also mobile platforms. While Silverlight has some limitations on this aspect. It mainly supports Windows and Max OS X. Silverlight looks to be as far as Microsoft has ever gone as a company to embrace cross-platform and yet they still fail to give full support for Linux.[3] However, a newly developed project, called Moonlight by Mono open source project sponsored by Novell, allows Linux users to run Silverlight applications on Linux, provide a Linux SDK to build Silverlight applications and reuse the Silverlight engine built by Mono for desktop applications. [4] Written with a combination of C++ and C# code, Moonlight (Linux supports for Silverlight 1.0) was first released in May, 2008.[5] In the mobile sector, Silverlight is spreading to mobile platform by building various applications on mobile devices. Mobile platforms supported by Silverlight are Windows Mobile and Symbian (partner with Nokia).

Programming tool

Microsoft provides a handful amount of programming tools to support its Silverlight. Visual Studio 2005 (supports Silverlight 1.0) and 2008 (supports Silverlight 1.0 and Silverlight 2.0), and Expression Studio are the main programming tools that developers can use to build Silverlight animations/applications. Programming languages which are supported by Silverlight are JavaScript, Visual Basic, and C#.

Adobe also provides its own developing tools to assist developers in creating Flash animations/applications. Such tools are Adoble Flash and Adobe Flex. However, compare to Silverlight, programming language supported by Flash is very limited. It is only supported by ActionScript.


According to a survey given by Adobe System in June 2008, 99% of computer users have installed Flash Player. But until then, there was still no official statistics about Silverlight given by Microsoft.

This significant difference of market share between Flash and Silverlight may due to following reasons:

  • Silverlight was released as 1.0 in 2007 while Flash 1.0 was released in 1996. Flash already has sufficient time to grow, thrive and dominate the media plug-in market before Silverlight was born. One way for Microsoft to increase the number of Silverlight users is to include Silverlight in Internet Explorer.
  • Users choose to view content built in Flash and therefore need the plug-in. Since Silverlight is still new, there is relatively little knowledge of its existence (among non developers) and application created in it. Microsoft is providing more Silverlight content, such as the NBC online 2008 Olympic Games.

Although Silverlight has many advantages over Flash, it pales in front of Flash in terms of availability. It is not a unique Microsoft problem but a problem for every new offering when there is an incumbent who has a majority market share. Because Flash is so ubiquitous that it pushed QuickTime, Real Player, and windows movie files right out of the web space. As a juvenile in market, Silverlight may need a long time to get acceptance for itself.

See also