Puppeteer: Firefox is not supported in BiDi over CDP mode.

Firefox is requested in BiDi-over-CDP mode.

Error message

Firefox is not supported in BiDi over CDP mode.

How this error happens

BiDi-over-CDP is a Chrome adapter path. Selecting BiDi while treating Firefox’s endpoint as a CDP endpoint cannot create that adapter.

The snippets use the imported puppeteer instance.

await puppeteer.connect({
    browserURL: "http://127.0.0.1:9222",
    protocol: "webDriverBiDi",
});

How to fix

Use Firefox’s native WebDriver BiDi connection through the launcher.

const browser = await puppeteer.launch({
    browser: "firefox",
    protocol: "webDriverBiDi",
});

Things to keep in mind

The failing URL must refer to an old or incompatible Firefox CDP setup to illustrate the adapter mismatch. A normal Chrome URL can support the adapter, while a non-browser server fails earlier.

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