Umbraco is an open source content management system (CMS) platform for publishing content on the World Wide Web and intranets. It is written in C# and deployed on Microsoft based infrastructure. The open source backend is released under an MIT License while the UI is released under the Umbraco license.
Umbraco was developed by Niels Hartvig in 2000 and released as open source software in 2004. In 2009, CMS Wire described it as one of the leading .NET-based open source CMS systems. In 2010, with 1000 downloads a day, Umbraco was in the top five most popular downloads via the Microsoft Web Platform Installer, two places below its main rival DotNetNuke, and was the 12th most downloaded application from Codeplex, six places below DotNetNuke and 13 places higher than mojoPortal.