// the find
jenkinsci/jenkins
Jenkins automation server
Jenkins is the long-standing self-hosted CI/CD automation server, built in Java with a massive plugin ecosystem covering builds, tests, and deployments. It's for teams that need full control over their CI infrastructure and are willing to deal with the operational overhead that comes with it.
The plugin ecosystem (2000+) means almost any tool integration already exists, which is hard to replicate elsewhere. The core codebase is old but battle-tested across a huge range of production environments, and the project has genuine long-term maintenance with both weekly and LTS release lines. Pipeline-as-code via Jenkinsfile/Groovy gives real flexibility for complex build logic that config-file-only CI tools can't match.
The core is a 15+ year old Java codebase with legacy classes like Hudson.java still present, and the plugin API surface is huge and inconsistent in quality since plugins are maintained by different third parties with wildly varying levels of care. Groovy pipeline syntax has a steep learning curve and debugging failed pipelines is often miserable compared to newer YAML-based CI tools. Running and upgrading a Jenkins instance yourself is real operational work (plugin compatibility breakage, security patching, JVM tuning) that hosted CI competitors have mostly eliminated for users.