Jenkins

Jenkins is the granddaddy of CI/CD — the tool that taught the industry what continuous integration means. It runs in 80% of Fortune 500 companies, has 1,800+ plugins, and can automate literally anything. It's also a maintenance nightmare that makes teams want to cry.

Don't start a new project on Jenkins. GitHub Actions is free for public repos and integrates seamlessly with GitHub. GitLab CI is powerful for self-hosted GitOps. CircleCI and Buildkite are solid managed alternatives. Jenkins only makes sense if you need air-gapped environments, extreme customization, or your enterprise already has a dedicated Jenkins team.

The catch: Jenkins is losing market share (-8% YoY) for good reason. The UI is ancient. Security vulnerabilities are frequent. Plugin compatibility issues are constant. Self-hosting means you're managing Java, plugins, and the build server itself. Every new Jenkinsfile feels like writing XML with extra steps. If your company is on Jenkins, plan the migration to GitHub Actions or GitLab CI.