Jenkins

What is Jenkins?

Jenkins is an open-source automation server that's been the backbone of CI/CD for over a decade. It runs on your own infrastructure and can automate any part of the build, test, and deployment pipeline through a plugin-based architecture. It's self-hosted, which means you control everything — the hardware, the environment, and the data.

Pipelines

Jenkins pipelines are defined in a Jenkinsfile, a Groovy-based DSL that lives in your repository alongside your code. You can define stages, run steps in parallel, handle failures, and trigger downstream jobs. Declarative pipeline syntax makes the most common patterns straightforward; scripted pipeline gives you full Groovy when you need more control.

Plugin ecosystem

Jenkins has over 1,800 plugins covering integrations with almost every tool in the development stack — Git, Docker, Kubernetes, AWS, Slack, JIRA, and hundreds more. This extensibility is one of the main reasons it's still widely used despite newer alternatives. If you need to integrate with something, there's almost certainly a plugin for it.

The tradeoffs of self-hosting

Jenkins is powerful but comes with operational overhead. You're responsible for maintaining the server, managing plugins, handling updates, and dealing with the occasional plugin conflict. The configuration UI is showing its age compared to hosted alternatives like GitHub Actions or CircleCI. Most teams who stick with Jenkins do so because they need the control self-hosting provides, or because they have complex pipelines that are already built on it.

Pricing

Jenkins is free and open source. The cost is your own server infrastructure and the time to maintain it. CloudBees offers a supported commercial distribution if you want enterprise support without managing everything yourself.