Azure DevOps Server allows you to self host the same modern dev services available in Azure DevOps, including Boards (planning and tracking), Pipelines (CI/CD), Repos (Git repositories and centralized version control), Test Plans (manual and exploratory testing), Artifacts (package management and pipeline artifacts), and more.
Azure DevOps Server Express is free, simple to set up on both client and server operating systems, and supports all the same features as Azure DevOps Server. The only difference is that it is limited by licensing agreements to five or fewer active users.