MCP vs WebMCP
Product engineer: Ship an MCP server for API work; add WebMCP on pages where the user is present. Developer-platform lead: WebMCP is a draft in origin trial; MCP has dated spec revisions. Agent builder: WebMCP tools need a browser agent; most chat clients reach MCP servers instead.
The sourced difference
MCP runs over stdio or Streamable HTTP to a server; WebMCP registers tools inside a web page through document.modelContext, so only an agent running in the browser can call them. (MCP: MCP transports overview, 2026-07-28, read 5 November 2026; WebMCP: webmachinelearning/webmcp, read 5 November 2026 and Cloudflare changelog: Browser Run adds WebMCP to Kitesurf, moves to document.modelContext (28 Sep 2026), read 5 November 2026)
Verdicts by reader
| Reader | Verdict |
|---|---|
| Product engineer | Ship an MCP server for API work; add WebMCP on pages where the user is present. |
| Developer-platform lead | WebMCP is a draft in origin trial; MCP has dated spec revisions. |
| Agent builder | WebMCP tools need a browser agent; most chat clients reach MCP servers instead. |
Side by side
| Aspect | MCP | WebMCP |
|---|---|---|
| Maintainer | MCP maintainers under the Agentic AI Foundation | W3C Web Machine Learning Community Group (editors from Microsoft and Google) |
| What it is | A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. | A browser API that lets a page register JavaScript functions as tools, with descriptions and schemas, that an in-browser agent can call. |
| Status and version | Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. | Draft specification; Chrome and Edge test it in an origin trial, Brave behind a flag, no Firefox or Safari implementation (nekuda FAQ, October 2026). |
| What it does not do | Does not grade servers, verify registry entries, or prescribe a .well-known discovery file in the 2026-07-28 core spec; server cards are still Working Group work. | Does not work without a browser agent that reads the page; does not replace a server-side MCP endpoint; the declarative form-based API is only being explored. |
Read the full entries: MCP and WebMCP.
Seen in the shared crawl
| Path | Top 10,000 found | Ora leaderboard found |
|---|---|---|
/.well-known/mcp.json | 19 of 7,470 (0.25%) | 66 of 3,366 (1.96%) |
A path counts only when the answer is the right kind of document. Many sites answer these paths with an ordinary web page, which is not counted. See the census.
The shared crawl looks for WebMCP in the initial HTML of each home page. It found a WebMCP hint on 25 of 7,545 home pages in the Tranco top 10,000 and on 59 of 3,393 on Ora's leaderboard.