While CodePlex once encompassed a wide variety of projects, including SQL Server, WPF and Windows Forms-related projects, its major activities were focused on .NET Framework (including ASP.NET) and SharePoint. The most prominent and used project that was born inside CodePlex, the AJAX Control Toolkit, is a joint project between the community and Microsoft.
The initial beta started in May 2006, with the final release a month later in June. A new version of the website was released every three weeks adding additional features and updates.
In 2010, an unrelated CodePlex Foundation was renamed Outercurve Foundation to clear up confusion that there was a direct relationship between the foundation and CodePlex, which is solely owned and run by Microsoft.
Since January 22, 2010, Mercurial distributed source control system has been supported as well, and this support has been enhanced. On March 21, 2012, CodePlex announced the support of Git as a source control option.
On March 31, 2017, Microsoft announced the discontinuation of CodePlex. The original plan was to make CodePlex read-only in October 2017 before finally shutting it down on December 15, 2017. Microsoft partnered with GitHub to allow projects to be migrated to the service. The site eventually was shut down, and a full backup was made. An [archive] is avaliable as a lightweight site to browse the projects that remain, in a read-only mode. The projects can be downloaded, and can also be transferred to GitHub ot a similar place.