How Duolingo uses GitHub

Duolingo empowers its engineers to be force multipliers for expertise with GitHub Copilot.

Key metrics:

25% increase in developer speed with GitHub Copilot
1 minute set-up time for largest repo with Codespaces
67% decrease in median code review turnaround time
70% increase in pull requests

Woman using the Duolingo language learning app.

Play video: How GitHub Copilot Optimizes Duolingo's Language Teaching

Organization: Duolingo | Location: Pittsburgh, PA | GitHub Seats: 300

The Challenge

Learning a language can be difficult and expensive. In 2011, Duolingo set out to change this by offering a free way to learn another language. Now with more than 500 million users, Duolingo has gathered unprecedented data insights into how people learn.

To scale its mission, Duolingo's developers needed to work alongside teams of language learning scientists, machine learning engineers, and AI experts. But inconsistent standards and workflows limited developer mobility and efficiency, preventing the company from expanding its content and delivering on its core mission.

The Solution

Duolingo relies on GitHub Enterprise to keep its developers nimble and focused, leveraging GitHub's APIs and tools like Codespaces and GitHub Copilot.

A neon sign at Duolingo headquarters reading

Standardizing Workflows with Custom Integrations

Duolingo has used GitHub for source code management since 2011. Initially, the company relied on different third-party products like Gerrit and PullApprove for code review, leaving its three primary repositories with widely varying cultures and pull request processes. This prevented developers from easily moving between repositories.

As GitHub added new functionality, Duolingo adopted it and moved off third-party tools. When Duolingo's needs differed from offered functionality, the company turned to GitHub's APIs to standardize workflows across its repos and projects using a custom GitHub bot implementation. One Slack integration dropped the median turnaround time for code review from three hours to one.

"GitHub enables us to enforce consistency and a standardized engineering culture that makes internal mobility easier," explains Jonathan Burket, senior engineering manager at Duolingo.

Since building out this integration, Duolingo has moved toward a microservice architecture and grown from three repositories to 400. The integration has made it simple for teams to contribute to each other's projects and has even allowed non-technical employees to make small code changes without jeopardizing quality.

"GitHub has one of the more powerful APIs that I've worked with," says Art Chaidarun, principal software engineer at Duolingo. "It allows us to build whatever we need ourselves so that we can focus on our actual business needs and business logic, rather than building infrastructure that GitHub can handle."

Accelerating Development with GitHub Copilot

Duolingo has accelerated its workflow with GitHub Copilot, an AI-powered pair programmer that provides autocomplete-style suggestions to developers while they code. The tool offers two ways for developers to receive suggestions: by starting to write the code they want to use or by writing natural language comments that describe what they want the code to do.

Duolingo CTO Severin Hacker notes that GitHub Copilot is quick and easy to adopt for companies already using GitHub and delivers immediate benefits, especially for enterprises with sprawling codebases.

"GitHub Copilot works with all of our other code development tools, and enabling it across the entire organization is as simple as checking a box," says Hacker. "A tool like GitHub Copilot is so impactful at large companies because suddenly engineers can make impactful changes to other developers' code with little previous exposure."

Burket sees this as enabling developers to do their best work instead of getting caught up on details.

"GitHub Copilot stops you from getting distracted when you're doing deep work that requires a lot of your brain power. You spend less time on routine work and more time on the hard stuff. With GitHub Copilot, our developers stay in the flow state and keep momentum instead of clawing through code libraries or documentation."

GitHub Copilot has increased developer productivity by limiting context switching and reducing the need to manually produce boilerplate code. For developers new to a specific repository or framework, Burket estimates at least a 25% increase in developer speed, and a 10% increase for those already familiar with that codebase.

"GitHub Copilot is unique in the sense that it looks at the context of the rest of your work and incorporates that context into its recommendations. Other tools don't have that contextual awareness," says Hacker. "I don't know of anything available today that's remotely close to what we can get with GitHub Copilot."

Streamlining Setup with Codespaces

Duolingo has also found efficiency and consistency in Codespaces, GitHub's cloud-based development environment. When some developers had issues running Docker locally on their new Apple M1 machines, Codespaces offered a way to skip local environment troubleshooting and provide 1-click environment setup.

"With Codespaces, you don't need to waste a day or a week setting up each individual repository. Instead, you can get started within a few minutes," says Chaidarun. Now, setting up Duolingo's largest repo takes just one minute, as opposed to hours or even days before Codespaces. "Codespaces is great for maintenance too. When a developer gets into a weird state, they can just rebuild their Codespace to start fresh and get back to work. Otherwise, they might spend hours trying to fix what went wrong with their environment."

Codespaces has enabled teams to configure a standardized, yet customizable environment, making it easy for Duolingo to onboard developers faster into new projects.

Impact

Whether GitHub Copilot, Codespaces, or custom integrations built with GitHub's APIs, GitHub allows Duolingo's developers to spend more time on improving the product experience and developing new apps and learning content, instead of getting distracted dealing with daily minutiae.

"Engineering time is the most valuable resource at Duolingo," says Chaidarun. "Making the best use of that time with the help of GitHub Copilot and Codespaces enables us to reach our goals faster."