SeleniumHQ/selenium · error · WebDriverException

Unable to find url to connect to from capabilities

Error message

Unable to find url to connect to from capabilities

What it means

Raised by start_devtools() when no CDP websocket URL could be obtained — neither from the se:cdp capability nor from _get_cdp_details(). Without a websocket endpoint, Selenium cannot open a DevTools channel. This is the catch-all 'no endpoint found' failure for the CDP code path.

Source

Thrown at py/selenium/webdriver/remote/webdriver.py:1157

        if value.upper() in allowed_values:
            self.execute(Command.SET_SCREEN_ORIENTATION, {"orientation": value})
        else:
            raise WebDriverException("You can only set the orientation to 'LANDSCAPE' and 'PORTRAIT'")

    def start_devtools(self) -> tuple[Any, WebSocketConnection]:
        global cdp
        import_cdp()
        if self.caps.get("se:cdp"):
            ws_url = self.caps.get("se:cdp")
            cdp_version = self.caps.get("se:cdpVersion")
            if cdp_version is None:
                raise WebDriverException("CDP version not found in capabilities")
            version = cdp_version.split(".")[0]
        else:
            version, ws_url = self._get_cdp_details()

        if not ws_url:
            raise WebDriverException("Unable to find url to connect to from capabilities")

        if cdp is None:
            raise WebDriverException("CDP module not loaded")

        self._devtools = cdp.import_devtools(version)
        if self._websocket_connection:
            return self._devtools, self._websocket_connection
        if self.caps["browserName"].lower() == "firefox":
            raise RuntimeError("CDP support for Firefox has been removed. Please switch to WebDriver BiDi.")
        if not isinstance(self.command_executor, RemoteConnection):
            raise WebDriverException("command_executor must be a RemoteConnection instance for CDP support")
        self._websocket_connection = WebSocketConnection(
            ws_url,
            self.command_executor.client_config.websocket_timeout,
            self.command_executor.client_config.websocket_interval,
        )
        targets = self._websocket_connection.execute(self._devtools.target.get_targets())
        for target in targets:

View on GitHub (pinned to aa36b38e69)

Solutions

  1. Launch Chrome/Edge with --remote-debugging-port=9222 (or rely on Selenium Manager/Grid to inject it).
  2. Ensure the browser actually exposes /json/version with a webSocketDebuggerUrl field.
  3. If using Selenium Grid, confirm it injects se:cdp / se:cdpVersion; otherwise enable the debugger address in goog:chromeOptions.
Defensive patterns

Strategy: validation

Validate before calling

ws_url = driver.capabilities.get('se:cdp') or driver.capabilities.get('se:cdpVersion')
if not ws_url:
    # ensure debugger address exists for local derivation
    opts = driver.capabilities.get('goog:chromeOptions') or {}
    if not opts.get('debuggerAddress'):
        raise RuntimeError('No CDP endpoint; launch Chrome with --remote-debugging-port')

Try / catch

from selenium.common.exceptions import WebDriverException
try:
    devtools, conn = driver.start_devtools()
except WebDriverException as e:
    if 'Unable to find url' in str(e):
        # relaunch browser with remote debugging enabled
        raise

Prevention

When it happens

Trigger: Calling driver.start_devtools() (or bidi_connection) when caps has no se:cdp AND _get_cdp_details() returns an empty/None websocket_url. This happens when the browser's /json/version endpoint did not expose webSocketDebuggerUrl, or when caps lack the chrome/edge debugger address entirely.

Common situations: Running against a headless or containerized Chrome/Edge whose DevTools endpoint is not exposed, a remote driver that strips debugger options, or a browser that was launched without --remote-debugging-port. Also seen when se:cdp is absent and the local debugger lookup fails.

Related errors

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/06aa8cb37c461d88. Report an issue: GitHub.