Formerly Citrusbyte, we are now Theorem. Read our story.

History of Microsoft Silverlight

In 2007 Microsoft introduced a revolutionary new set of developer tools to facilitate web development. Its goals were to offer cross-browser compatibility with a focus on using UI elements such as animation and video.

Trends in tooling

When Microsoft Silverlight was released, browsers and computers utilized client-side logic and associated plugins to drive rich web experiences. This was reflected with three main client-side technologies: Java, Flash, and Silverlight.

These rich plugins offered many features then not available to users of browsers without plugins. Especially with the emergence of streaming video systems platforms. Netflix, and Amazon Video both used Silverlight, Youtube utilized Flash.


Browser-side plugins have several disadvantages, and over time trends for tooling drastically shifted from being dominated by Java, Flash, and Silverlight to almost exclusively Javascript based logic in the form of asynchronous javascript libraries (AJAX) and HTML5.

This trend in tooling has provided a number of advantages that have driven it’s adoption, specifically ubiquitous browser support, especially on mobile devices where plugins are less feasible than on desktop platforms, and security.

As a result Silverlight, and Flash are effectively being eliminated from use.

Client Site Programming Languages in 2019


Percentages of websites using various client-side programming languages. A website might use more than one client-side programming language., 15 March 2019

Microsoft ends development and support

In July of 2015, Microsoft announced the support end date for Silverlight 5 to be October 2021.

In practice, support among browsers has already ended. Silverlight is no longer supported in Google Chrome (since September 2015), and in Firefox (since March 2017). There isn’t event a Silverlight plugin available for Microsoft’s own Edge platform.

This leaves older versions of Internet Explorer to be the only browsers feasible for running Silverlight applications. These older versions of Internet Explorer (IE) create their own support problems in the form of limited operating system compatibility, and lack of security related updates. Most companies are systematically rolling off older versions of IE for this reason.

Modernization Strategies

Modernizing a legacy system is a great opportunity for enhancement and cost-saving measures, such as modern DevOps and infrastructure backend support systems and even entirely new ways of using technology - e.g. mobile interfaces.

With the sunset of Silverlight quickly approaching, time is of the essence for modernizing existing applications to utilize modern techniques in browser-related tooling.

At Theorem we provide modernization services for our customers with legacy Silverlight applications. If you have systems and applications built with Silverlight please get in touch with us. We can provide a complimentary assessment of your legacy systems and develop an integrated modernization plan.

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