Basics > Overview

This document provides a summary of continuous integration, how CircleCI enables engineering teams with automation, CircelCI case studies, and free trial information in the following sections:

What is Continuous Integration?

Continuous integration is a practice that encourages developers to integrate their code into a master branch of a shared repository early and often. Instead of building out features in isolation and integrating them at the end of a development cycle, code is integrated with the shared repository by each developer multiple times throughout the day.

Continuous Integration is a key step to digital transformation.

Every developer commits daily to a shared mainline.
Every commit triggers an automated build and test.
If build and test fails, it’s repaired quickly - within minutes.

Improve team productivity, efficiency, happiness. Find problems and solve them, quickly. Release higher quality, more stable products.


CircleCI - Our mission is to empower technology-driven organizations to do their best work.
We want to make engineering teams more productive through intelligent automation.

CircleCI provides Enterprise-class support and services, with the flexibility of a startup.
We work where you work: Linux, macOS, Android - SaaS or behind your firewall.
Leverage the opportunities created by your modern Git repos.
Set up in minutes out of the box, or fully customize to suit your needs.

The following video describes continuous integration, provides a demo of the application, and includes a discussion of continuous deployment.


After a software repository on GitHub or Bitbucket is authorized and added as a project to, every code change triggers automated tests in a clean container or VM. CircleCI then sends an email notification of success or failure after the tests complete. CircleCI also includes integrated Slack, HipChat, Campfire, Flowdock, and IRC notifications. Code test coverage results are available from the details page for any project for which a reporting library is added.

CircleCI may be configured to deploy code to various environments, including AWS CodeDeploy, AWS EC2 Container Service (ECS), AWS S3, Google Container Engine (GKE), and Heroku. Other cloud service deployments are easily scripted using SSH or by installing the API client of the service with your job configuration.

Customer Use Cases

The following section outlines two examples of real-world CircleCI usage.


Coinbase runs CircleCI Enterprise behind their firewall for security and reliability. The Coinbase case study report reveals that using CircleCI reduced their average time from merge to deploy in half, reduced operations time spent on continuous integration maintenance from 50% of one person’s time to less than one hour per week, and increased developer throughput by 20%.


Sony Japan continuously deploys microservices built with Go and Docker in minutes using the CircleCI hosted application as described in the SONY case study report. The NG-Core services are written in Go, packaged into Docker containers, pushed to Docker Hub, then deployed to AWS Elastic Beanstalk. In detail, the process looks like this:

  1. The developer commits and pushes to GitHub
  2. CircleCI receives a hook from GitHub, triggering a build
  3. CircleCI pulls down the latest code, compiles the Go binaries, and creates a deployable image with docker build
  4. Unit and integration tests are run, including some tests that use the final Docker image
  5. The Docker image is pushed to Docker Hub, and a new deployment is triggered on Elastic Beanstalk
  6. A final live system test is run after the deployment

The entire build and test processes each run about 5 minutes, and when deployments are triggered they run about an additional 10 minutes. The NG-Core team started development using this process in May of 2014, has been in production since January 2015, and they are extremely happy with the setup.

See the CircleCI Customers page for the complete set of case studies for companies large and small who are using CircleCI, including the following:

Free Trial Options

CircleCI provides a free trial with the following options:

Open Source

See Building Open Source Projects for information about free containers for public open source projects.