OpenUI
A code-like rendering spec for Generative UI
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What is OpenUI?
OpenUI is a full-stack Generative UI framework that lets AI applications respond with rendered user interfaces instead of plain text. It combines a compact streaming-first language, a React runtime, and ready-to-use chat interfaces so LLM output can become live UI as it streams.
The workflow is built around four pieces: you define a component library, OpenUI turns that library into a system prompt, the model returns OpenUI Lang, and a parser plus renderer convert that output into UI. The site emphasizes that the library is the contract between your app and the AI, which helps keep outputs predictable and typed.
OpenUI Lang is designed to be token-efficient and stream-friendly compared with JSON. The site says it can use up to 67.1% fewer tokens than json-render and offers 3x faster rendering than json-render, with native streaming so interfaces can appear in real time.
It is meant for developers building conversational apps, dashboards, web apps, mobile apps, and other interactive AI experiences. The site also highlights compatibility with multiple LLMs, UI libraries, and frameworks, including React, React Native, Vue, Vercel AI SDK, LangChain, CrewAI, OpenAI Agents SDK, and Anthropic Agents SDK.
OpenUI pricing
Pricing model: Freemium
The website presents OpenUI as an open source toolkit and does not show paid plans or a subscription tier on the pages reviewed. It emphasizes that the toolkit is available to install and use, with the main experience centered on the open standard, docs, and component libraries. No free-tier limitations, usage caps, or included paid-plan features are listed on the site pages reviewed.
OpenUI pros
- Open source toolkit
- Full-stack Generative UI framework
- Streaming-first language
- Token-efficient compared with JSON
- Up to 67.1% fewer tokens than json-render
- 3x faster rendering than json-render
- Real-time UI rendering
- Built-in React runtime
- Ready-to-use chat interfaces
- Supports conversational apps
- Supports dashboards and web apps
- Supports mobile apps
- Works with multiple LLMs
- Compatible with multiple UI libraries
- Compatible with multiple agent frameworks
- Live data support at runtime
- Tool and MCP server querying
- Interactive components with reactive state
- Safe by default with no arbitrary code execution
- Cross-platform support including React Native and Vue
OpenUI cons
- Requires defining a component library first
- Depends on correct prompt generation for reliable output
- Requires parsing and schema validation for custom libraries
- OpenUI Lang is a specialized format to learn
- Best fit is for structured interactive UI, not plain text
- Chat-optimized library is single-card and vertically stacked
- Some advanced behavior depends on runtime tool and MCP access
- Performance claims are benchmark-specific to json-render
Frequently asked questions about OpenUI
What is OpenUI?
OpenUI is a full-stack Generative UI framework that turns LLM output into rendered interfaces. It uses a compact OpenUI Lang format, a React runtime, and built-in libraries so AI apps can display UI instead of only text.
How does OpenUI work?
You define a component library, OpenUI generates a system prompt from that library, the model responds in OpenUI Lang, and the parser and renderer turn that response into live UI. The framework is designed so the library acts as the contract between your app and the AI.
What is OpenUI Lang?
OpenUI Lang is the line-oriented language OpenUI uses for model output. It is designed to be compact, streaming-friendly, and more predictable than verbose JSON when generating UI structures.
What built-in libraries does OpenUI include?
OpenUI ships with two ready-to-use libraries through @openuidev/react-ui. One is a general-purpose library for standalone rendering and non-chat interfaces, and the other is a chat-optimized library with chat-specific blocks and a single-card vertical layout.
What kinds of apps is OpenUI for?
OpenUI is aimed at developers building conversational apps, dashboards, web apps, mobile apps, bottom trays, and other interactive AI-driven interfaces. The site positions it as a way to make AI apps respond with the UI users need, not just text.
Which models and frameworks does OpenUI support?
The site says OpenUI works across multiple LLMs, including OpenAI, Anthropic, Gemini, Mistral, xAI, and DeepSeek. It also says it works with frameworks like Vercel AI SDK, LangChain, CrewAI, OpenAI Agents SDK, and Anthropic Agents SDK.
Does OpenUI support real-time streaming?
Yes. OpenUI is built with native streaming so UI can render progressively as model output arrives, rather than waiting for the entire response to finish.
Is OpenUI safe to use in production?
The site says OpenUI is safe by default because it does not allow arbitrary code execution. It also uses schemas and parsing to validate structured output before rendering it.
Can OpenUI use live data?
Yes. The site says OpenUI supports live data by querying tools and MCP servers at runtime, which lets the generated UI reflect current information.
What platforms does OpenUI work on?
OpenUI says it works across platforms, including React, React Native, and Vue. That makes it suitable for web and mobile UI generation in different frontend stacks.