On March 31, 2017 Brian Harry announced that CodePlex is shutting down. But we should have known this was coming, as over the past few years Microsoft had been running their open source projects on GitHub. In his blog post, Harry wrote that there has been significant decrease in activity at CodePlex, with commits to less than 350 projects over a month’s time.
As of now, no new CodePlex projects can be created, but you can still work on existing CodePlex projects. But only until October 2017, when Microsoft will make the CodePlex service read-only.
CodePlex will be shut down on December 15, 2017, but Microsoft plans back up all of the content and launch a read-only archive of the published projects. So you’ll still be able to search and download project files.
The tough part of this is going to be for those with projects that were SEO’d. Microsoft says they will do what they can with redirects of existing URLs, but I would not rely on that to maintain project traffic.
Microsoft is providing information and support for source code migration efforts. So if there is an important project on CodePlex, you may want to get started now migrating the project over to another source code repository, like GitHub.