What is Persona.js?

Persona is a lightweight, open-source AI chat UI library that embeds into any website using pure JavaScript. Unlike React-based chat frameworks, Persona is framework-free, backend-agnostic, and WebMCP-native, so your assistant can discover and execute tools exposed by the parent page. It adds streaming chat, voice, theming, and interactive copilot experiences without rebuilding your frontend or writing bespoke APIs.

Who it's for

• Frontend developers who want to drop an AI assistant into any website without rewriting their stack or learning a new framework
• Product teams shipping agentic experiences that need to operate page tools like search, carts, bookings, or forms directly
• Startups and indie builders looking for a fast, embeddable chat UI that works with any backend and any hosting setup

Key features

Three layout modes

Persona offers floating, docked, or fullscreen UX. Switch between a corner launcher for support, a side copilot that resizes your layout, or a full-height assistant that owns the page — all by changing a single launcher config value.

WebMCP-native tool execution

Expose page actions, search, carts, bookings, and forms as WebMCP tools. The agent drives them directly with built-in user approval, requiring no backend integration for tool discovery and execution.

Shadow DOM isolation

Shadow DOM rendering and prefixed CSS keep widget and host styles fully separate. Drop Persona into any page and nothing leaks in or out, preserving your existing design system.

Pluggable streaming transport

SSE streaming with pluggable parsers adapts any request or event shape using customFetch and parseSSEEvent. This works with any backend that supports server-sent events.

What stands out

Persona is the first agent UI library that treats the browser as a first-class runtime, not just a display surface.

Most chat UIs are passive — they display text and wait for API responses. Persona flips that by making the agent an active participant in the page. It discovers tools exposed by the parent page, executes them with user approval, and streams responses in real time. This means your assistant can search your docs, add items to a cart, or fill a booking form without you writing a single backend endpoint for those actions.

Worth checking out if…

You want to add an AI assistant to any website — from a static HTML page to a modern SPA — without adopting a new framework or rebuilding your frontend. If you need streaming chat, voice, theming, and agentic tool use that works with any backend, Persona delivers a production-ready solution in a few lines of code.