List open tabs (index, title, URL). Selected tab is marked.

Open new tab at URL. Returns tab index.

Navigate selected tab to URL.

Select active tab by index, URL, or title. Index takes precedence.

Close tab by index.

Get the visible text of the page (document.body.innerText). Caps at maxLength (default 20000 chars); saveTo saves the full text to a file.

Capture DOM snapshot with stable UIDs. Retake after navigation. Output caps at maxLines (default 100); scope with selector or dump the full tree with saveTo.

Resolve UID to CSS selector. Fails if stale.

Clear snapshot cache. Usually not needed.

Click element by UID. Set dblClick for double-click.

Hover over element by UID.

Fill text input/textarea by UID.

Drag element to another (HTML5 drag events).

Fill multiple form fields at once.

Upload file to file input by UID.

Capture page screenshot as base64 PNG.

Capture element screenshot by UID as base64 PNG.

List downloads tracked since startup, including status and saved file path.

Clear the tracked downloads buffer.

Control how downloads are handled: allow (save silently to the default download directory), deny (cancel), or reset to default. Avoids the native save-file dialog. Requires a recent Firefox.

Accept browser dialog. Provide promptText for prompts.

Dismiss browser dialog.

Navigate history back/forward. UIDs become stale.

Set viewport dimensions in pixels.

Retrieve Firefox output (stdout/stderr including MOZ_LOG, warnings, crashes, stack traces). Returns recent output from the capture file. Use filters to focus on specific content.

Get information about the current Firefox instance configuration, including binary path, environment variables, and output file location.

Restart Firefox with different configuration. Allows changing binary path, environment variables, and other options. All current tabs will be closed.

Install a Firefox extension using WebDriver BiDi webExtension.install command. Supports installing from archive (.xpi/.zip), base64-encoded data, or unpacked directory.

Uninstall a Firefox extension using WebDriver BiDi webExtension.uninstall command. Requires the extension ID returned by install_extension or obtained from list_extensions.

Start recording a screencast (video) of the current page viewport, saving the output to a file in the downloads directory. Returns a screencast id to pass to screencast_stop. Multiple recordings can run at once.

Stop an in-progress screencast recording started with screencast_start and finalize the video file. Returns the path to the saved file.

Run a JS function in the page and return its result. Prefer this for targeted reads (a value, text, computed style, whether an element exists) instead of a full take_snapshot. Use the UID interaction tools for clicking, typing, and filling.