Published: March 11, 2026
In February, we announced that WebMCP is available for the early preview program. As AI agents become more common in browsers, we've heard web developers ask this question: "Will WebMCP replace Model Context Protocol (MCP)?"
While I can see why you've asked this question, it's based on a misunderstanding. You don't have to choose between MCP and WebMCP to create an agentic experience. WebMCP is not an extension or a replacement of MCP. Instead, WebMCP and MCP address different needs. WebMCP lets you clarify the purpose of application features and provide a browser agent with additional capabilities to interact with your website.
A good analogy is the difference between a company's customer service call center and an in-store expert.
- MCP is available on any platform at any time. It can pull up data and handle core tasks as needed.
- WebMCP is available only on your website. Websites are typically user interfaces (UIs) designed for humans, not machines. WebMCP helps agents better understand UI.
Together, they help agents accomplish personalized tasks on behalf of human users.
Functions and purpose
Both technologies share the same philosophy: to create a standardized and reliable way for applications to expose their tools to AI agents.
In practice, this includes:
- Structured tool discovery: They provide a machine-readable way for an agent to ask, "What can you do?" and get a clear list of available tools, their parameters, and their purpose.
- Predictable execution: They replace guesswork with explicit function calls. An agent calls a defined tool. This leads to a predictable outcome, unlike simulating a click pattern that might change.
- Clear intent: They explicitly declare capabilities. Without WebMCP and MCP, agents guess what action to take based on an understanding of the UI. With WebMCP and MCP, agents can know with certainty how a given feature should work, without needing to infer actions from UI elements.
The key difference between them is where the application functionality lives.
MCP is for backend
The Model Context Protocol (MCP) is a standard that connects AI agents (whether browser-based or not) with external systems, including data sources, tools, and workflows. The protocol is universal, often uses JSON-RPC, and is implemented through language-specific SDKs, such as Rust, Python, and TypeScript.
WebMCP is for the frontend
WebMCP is a proposed browser standard with two APIs that exclusively interact with a browser's built-in agent. You can implement these APIs with JavaScript or HTML attributes. The browser acts as the communicator between your website and the agent.
Consider WebMCP a set of "MCP-inspired" APIs, rather than a direct JavaScript implementation of MCP. WebMCP is purpose-built for the browser and omits various server-side concepts, such as resources.
Control how agents access your website
WebMCP lets you control how agents interact with your website. This has several key advantages:
- Speed and reliability: Because WebMCP uses the browser's internal systems, the communication between the client and the tool is nearly instant. You don't have to wait for a round trip to a remote server.
- Built to last: WebMCP tools connect to application logic, not design. This means you can redesign your website without breaking an agent's ability to correctly interact with it.
- You're in control: You clearly define the preferred way for an agent to interact with your site, instead of hoping the agent finds the right button to click. You define your application's logic in a way the agent can understand, guiding them directly rather than hoping they infer actions from the UI.
Control UI access
To understand the difference, consider, "Who owns the UI?" MCP apps render your application's UI within the agents UI. Your interface must conform to these constraints, and it requires a new, separate application.
WebMCP helps agents interact with your existing website in real-time. It can access live session data, cookies, and DOM elements that are available only in a live browser tab. Instead of your application being a guest within an agent, the agent is a guest on your platform.
Importantly, WebMCP tools are ephemeral. They exist only when your page is open. Once the user navigates away from your site or closes the tab, the agent can no longer access your site or take actions.
Use WebMCP and MCP
When choosing the right solution for specific features or functions, consider context and availability:
| MCP | WebMCP | |
|---|---|---|
| Purpose | Makes data and actions available to agents anywhere, anytime. | Makes a live website ready for instant interaction with agents when a user visits the site. |
| Lifecycle | Persistent (server and daemon) | Ephemeral (tab-bound) |
| Connectivity | Global (desktop, mobile, cloud, web) | Environment-specific (browser agents) |
| UI interaction | Headless and external | Browser-integrated and DOM-aware |
| Discovery | Agent-specific registration flows | Tools registered on the web page during the user's visit. |
| Use case | Performs background API actions. | Navigates and actuates on a live web UI. |
The most effective agentic applications use both MCP and WebMCP to benefit from the strengths of both technologies.
- Manage core logic with MCP: Your MCP server acts as a foundational service layer. It handles the core business logic, data retrieval, and background tasks. This ensures your service is platform-agnostic and always available to agents.
- Build a contextual UI with WebMCP: WebMCP is the final step, a connection for agents directly to your website. It's designed for contextual, in-browser interactions, letting an agent act on the user's behalf with speed and reliability while the user has your website open.
Consider MCP and WebMCP as partners, not opponents. WebMCP provides a high-fidelity way for a browser-based AI agent to interact with the specific world the user sees in their tab.
What's next?
Ready to make your website agent-ready? You can start experimenting with WebMCP today by joining the Early Preview Program.
Your feedback is crucial in shaping the future of this standard.