On June 29, 2021, GitHub announced GitHub Copilot in a post titled “Introducing GitHub Copilot: your AI pair programmer.” GitHub described it as a technical preview of a tool that helps developers write code by suggesting completions and entire functions directly inside the editor as a person types. The announcement noted it was developed with OpenAI and was particularly effective with languages including Python, JavaScript, TypeScript, Ruby, and Go.
Copilot was powered by OpenAI Codex, a model trained on code. The accompanying research paper, “Evaluating Large Language Models Trained on Code” (submitted July 7, 2021), authored by Mark Chen, Jerry Tworek, and a large team at OpenAI, documented how a large language model could be trained and measured on programming tasks. It introduced systematic ways to evaluate whether generated code actually works.
Copilot marked the first widely visible product to bring large language models into everyday software development. It moved AI code generation from a research curiosity into a tool used by working developers, and it set the stage for the agentic coding tools that followed later in the decade.