What is GitHub Actions? Automated CI/CD for GitHub

GitHub Actions is a platform built into GitHub that automates software building, testing, and deployment. GitHub, owned by Microsoft, is a hosting service for software development using Git, an open source version control and collaboration program developed by Linus Torvalds. Git and GitHub are already used by many programmers and software shops as the basis for their development practices, including the automated continuous integration and continuous delivery pipelines that carry projects through the build, test, and deploy cycle. GitHub Actions provides GitHub users with what GitHub calls an "API for cause and effect." You can use the platform to automate all sorts of behaviors based on various triggers.

GitHub introduced GitHub Actions in 2018. Because of GitHub's open nature, it's not the only tool that you can use to implement CI/CD automation for GitHub-based projects; others, such as Azure Pipelines and Jenkins, may be preferable in some situations. But because GitHub Actions is integrated with the GitHub platform as a whole, users don't need to worry about the underlying infrastructure. Its overall workflow is also designed with GitHub in mind, which will make it an attractive option for many. 

How GitHub Actions works

One of the best ways to understand how GitHub Actions works is to consider the terminology that describes its individual components. We'll start with the name, "GitHub Actions." We're following GitHub's lead in treating that as a singular noun ("GitHub Actions is..."), which names the platform as a whole. There's also a component of the platform called an "action" (small "a"), which we'll discuss shortly.

Now, let's look at some of the components of the platform:

Examples of GitHub Actions

The GitHub docs include examples to help you understand how GitHub Actions works. To start, you could test your code on a runner. Another example demonstrates how to work with GitHub Actions from the GitHub command-line interface.

An example that goes further—and that may be of particular interest in exploring the power of GitHub Actions—involves what GitHub calls a matrix strategy. In this type of workflow, you would use variables when defining a job in order to create multiple job runs that differ based on the values of the variables. As GitHub's in-depth example shows, this is a good way to automatically test your code against different language or operating system versions; you can change the values of the variables to choose new test environments.

Fireship.io has some more useful GitHub Actions examples for you to peruse, including demonstrations of how to publish a package to NPM when you create a new release; how to automatically send email, Slack, or Discord messages updating users on job progress; or how to schedule a background job at a specific time or at specific intervals.

Security best practices for GitHub Actions

If you're running GitHub Actions on code in a GitHub repo, you're almost certainly working with a distributed codebase, and that brings up security complications. GitHub recommends these best practices to ensure that your workflows are secure:

For more in-depth security information, check out GitHub's guide to security hardening for GitHub Actions.

Integrating GitHub Actions with other platforms

Because GitHub is a relatively open platform and GitHub Actions workflows are described in declarative YAML, there are a few ways you can integrate your GitHub Actions code with other platforms:

Do I need to pay for GitHub Actions?

GitHub Actions is free if your jobs execute on standard GitHub-hosted runners in public repositories, or if you host your runners yourself. If you're using a private repo, you get a certain amount of storage and compute time for free but must pay once you exceed those limits. There are also overall limits on the number of concurrent jobs you can run using GitHub-hosed runners, as well as on API requests per hour and workflow runtime. See the GitHub docs for more details.

Alternatives to GitHub Actions

There are other tools on the market that automate the CI/CD process and therefore occupy much of the same space as GitHub Actions. Perhaps one of the most prominent and mature is Jenkins, an open source offering that traces its roots back to 2004. Jenkins can work with GitHub repositories via plugins—as well as code in any number of other environments—and is generally quite flexible, although the learning curve may be steep compared to GitHub Actions.

In general, GitHub Actions' greatest strength is its tight integration with GitHub. Other hosting services have their own equivalents; GitLab has GitLab CI, for instance, and there is also AWS CodeCataylst actions. If you're using GitHub and you aren't already invested in a cross-platform tool like Jenkins, GitHub Actions is a logical choice for your automated CI/CD needs.