Apps SDK
The Apps SDK lets you build apps inside ChatGPT — full-stack experiences (auth, custom UI, network access) that users interact with through a conversation. Under the hood: every app is an MCP server with extra metadata telling ChatGPT how to render rich UI. The widget surface uses a content type called text/html+skybridge — ChatGPT renders the HTML in a sandboxed iframe alongside the conversation. The Apps SDK is the modern replacement for the older ChatGPT Plugins system (deprecated 2024) and a different surface from Custom GPTs. Sourced from developers.openai.com/apps-sdk.
- APPS.1 OpenAI Apps SDK, plainly sourced
Five-minute orientation to the OpenAI Apps SDK — what it is (a framework for building apps that run inside ChatGPT with rich UI), what it's not (Custom GPTs, GPT Actions, or the old plugins system), and how it uses MCP under the hood.
- APPS.2 MCP plugin for ChatGPT — the server side sourced
How to wire an MCP server so ChatGPT can discover and call it as a tool — registering UI templates, describing tools, returning structuredContent. Code primarily in TypeScript (the Python and TypeScript MCP SDKs share the same shape; this page uses the TypeScript scaffolding throughout).
- APPS.3 Widget rendering — text/html;profile=mcp-app and the iframe bridge sourced
The widget side of the OpenAI Apps SDK — how ChatGPT renders your HTML in a sandboxed iframe, the MCP Apps JSON-RPC bridge for tool I/O, the window.openai extension surface, and the CSP contract.