Flash vs Silverlight

Flash and Silverlight are web animation frameworks that allow browsers with appropriate plugins to display advanced animations on websites.

Flash was originally developed by Macromedia. It is now owned by Adobe after Adobe purchased Macromedia.

Silverlight is produced by Microsoft.

Popularity

Client

Flash is widely popular on the internet. Some statistics demonstrate that Flash is installed on 96% of all computers of internet users.

Silverlight is a much more recent addition to the field, and as such it has not had time to build much market share by comparison with Flash. Because it was actively pushed by Microsoft and thus used for streaming large events like the Olympics and the download size is intentionally kept small a lot of people have it installed without being aware of it.

Server

Flash is used to animate many web pages on the internet. Almost all streaming video and audio websites use Flash to stream their content. Silverlight is making some inroads however, because streaming is supposed to be cheaper and more efficient on Silverlight than on Flash. Because of fierce competition the supported codecs and licensing schemes of both offerings may change.

Portability

Versions of the Flash player currently work on Linux, FreeBSD, Windows, and MacOS X. Linux support is good for older versions, as is support for all versions on MS Windows and MacOS X. Though Adobe periodically releases a new Linux version (some time after MS Windows and MacOS X versions), certain version numbers are known to have stability issues on Linux. Adobe does not officially support Flash on FreeBSD at this time, so Flash support on FreeBSD is achieved by employing work-arounds or compatibility layers to make use of the Linux Flash players. This results in more stability problems on FreeBSD than one might encounter on Linux-based systems.

The Silverlight runtime is officially supported for Windows and Mac OS X. The Mono project provides Moonlight (open source implementation of the plugin) supported by Novell. In theory, this should provide roughly seamless portability across platforms that are supported by Mono.