GitHub Copilot
GitHub's AI completion tool — suggests code in your IDE based on file context and comments. Originally trained on OpenAI Codex (a GPT-3 derivative).
Launched June 2021 (preview), GA June 2022. Today Copilot runs Claude, GPT-4o, o1 and Gemini selectable per user. Copilot Chat (sidebar in VSCode/JetBrains/Visual Studio) added Q&A and refactor commands. Copilot Workspace (preview 2024) tackles whole features at once.
Triggered RIAA-style copyright debates ("memorising GPL code"). Competitors: Cursor, Codeium, Tabnine, JetBrains AI Assistant. Still dominates via GitHub integration and enterprise sales.