What is Jenkins?

Jenkins is an open-source automation server that helps developers build, test, and deploy software continuously. It runs tasks called “jobs” automatically whenever code changes, so you don’t have to do repetitive steps by hand.

Let's break it down

  • Open-source: Free for anyone to use, modify, and share.
  • Automation server: A program that runs other programs for you, like a robot that follows a recipe.
  • Build, test, and deploy: The three main steps in creating software - compiling code (build), checking it works (test), and sending it to users (deploy).
  • Continuously: Happens automatically every time new code is added, not just once in a while.
  • Jobs: Small, defined tasks (e.g., “compile this project”) that Jenkins executes.

Why does it matter?

Because software projects grow fast, doing everything manually becomes slow and error-prone. Jenkins speeds up delivery, catches bugs early, and lets teams focus on writing code instead of repetitive chores.

Where is it used?

  • A web-app company runs Jenkins to compile code, run unit tests, and push new versions to their staging servers after each commit.
  • A mobile-app team uses Jenkins pipelines to build Android and iOS apps, run UI tests on real devices, and upload the builds to the app stores automatically.
  • An infrastructure team employs Jenkins to provision cloud resources and run configuration-management scripts whenever a new environment is needed.
  • An open-source project uses Jenkins to verify pull requests, ensuring contributions don’t break the build before they are merged.

Good things about it

  • Works with almost any programming language or tool thanks to many plugins.
  • Provides visual pipelines that make complex workflows easy to understand.
  • Runs on many platforms (Windows, Linux, macOS) and can be hosted on-premise or in the cloud.
  • Strong community support and extensive documentation.
  • Enables “fail fast” by detecting problems early in the development cycle.

Not-so-good things

  • The plugin ecosystem can become messy; outdated plugins may cause stability issues.
  • Setting up and maintaining pipelines can be time-consuming for beginners.
  • The UI, while functional, feels dated compared to newer CI/CD tools.
  • Scaling to very large numbers of jobs may require additional infrastructure and tuning.