Read from primary sources · 17 September 2026 · nothing here is from memory
Which browsers support WebMCP, and what state the specification is in.
Every line below was read from the specification and its implementation table on the date above. A missing date means the source gives none.
The specification
Draft Community Group Report, W3C Web Machine Learning Community Group, dated 15 September 2026. The document states that it is not a W3C Standard and is not on the W3C Standards Track.
A Community Group Report is where a proposal is worked out in the open before anyone commits to shipping it. The shape can still change, and the implementing vendors say so.
Section 4.3, the declarative HTML form syntax, is unwritten. Its body says it is a TODO and defers to an explainer in the specification's repository. Demos that annotate form elements are ahead of the text.
Implementations
From implementation-status.md in the specification's
repository, maintained by the same group and the closest thing to an
authoritative list.
| Implementation | State |
|---|---|
| Chrome | Origin trial live in Chrome 149, running through 156. Also available locally behind a flag. |
| Edge | Origin trial live in Edge 150. |
| ChatGPT Desktop | Supported. |
| Brave | Experimental, in Leo. |
| Firefox | Under standards review. No support. |
| Safari | Under standards review. No support. |
An origin trial is a time-boxed opt-in: a site registers, receives a token, serves it in a meta tag or header, and the feature works for that origin until the trial ends. A trial can end without the feature shipping.
The API surface, as specified
Much secondary coverage gets this wrong. The specification and Chrome's documentation agree on the following.
document.modelContext.registerTool(tool, options), notnavigator.modelContext.- A tool requires
name,descriptionandexecute. Optional:title,inputSchemaas JSON Schema, andannotations. - Also on the same object:
getTools(),executeTool()andunregisterTool().
What our audit does with this
It reports and does not score. A paid audit reads the sampled pages and says whether any declares the WebMCP surface in a script body and whether an origin-trial token is present. It counts the token without decoding it, since reading it means trusting a registry we do not hold.
That does not confirm a working tool. Tools are registered at runtime and our collector reads bytes, so we report what the page declares, and the report says so.
What WebMCP is, and what it is not · the rubric we do score against · run a free scan