Jenkins (https://jenkins.io/) is one of the leading CI/CD tools out there. It is free and open source. It is an automation server written in Java and supports integration with various version control tools, such as Git, CVS, and SVN. Jenkins has a huge plugin ecosystem and this makes it one of the most flexible platforms. Jenkins can be used for building projects, running automated tests, automating deployment, and so on. It is available as an executable binary for various platforms and as Docker images. Blue Ocean is the latest UI interface for Jenkins, giving it a much-needed breath of fresh air. Jenkins has the concept of a pipeline, achieved by using multiple plugins and a Groovy DSL to define the CI/CD pipeline. Jenkins pipeline plugins provide a comprehensive DSL-based configuration that can be defined in a file called Jenkinsfile.