SeleniumHQ/selenium · error · WebDriverException

Can not connect to the Service {self._path}

Error message

Can not connect to the Service {self._path}

What it means

Raised by Service.start() after the driver process is running but the service never became connectable within the retry budget (70 iterations, ~30 seconds total, sleeping up to 0.5s each). The process did not exit (otherwise error 167 fires first), it simply never answered the W3C /status endpoint on its port. On failure the service is stopped automatically before re-raising.

Source

Thrown at py/selenium/webdriver/common/service.py:120

        Raises:
            WebDriverException: Raised either when it can't start the service
                or when it can't connect to the service
        """
        if self._path is None:
            raise WebDriverException("Service path cannot be None.")
        self._start_process(self._path)

        count = 0
        try:
            while True:
                self.assert_process_still_running()
                if self.is_connectable():
                    break
                # sleep increasing: 0.01, 0.06, 0.11, 0.16, 0.21, 0.26, 0.31, 0.36, 0.41, 0.46, 0.5
                sleep(min(0.01 + 0.05 * count, 0.5))
                count += 1
                if count == 70:
                    raise WebDriverException(f"Can not connect to the Service {self._path}")
        except BaseException:
            try:
                self.stop()
            except Exception:
                logger.error("Error stopping service after a failed start.", exc_info=True)
            raise

    def assert_process_still_running(self) -> None:
        """Check if the underlying process is still running."""
        return_code = self.process.poll()
        if return_code:
            raise WebDriverException(f"Service {self._path} unexpectedly exited. Status code was: {return_code}")

    def is_connectable(self) -> bool:
        """Check if the service is ready via the W3C WebDriver /status endpoint.

        This makes an HTTP request to the /status endpoint and verifies if it is ready to accept new sessions.

View on GitHub (pinned to aa36b38e69)

Solutions

1. Increase available CPU/memory on the host or container; slow startup is the most common cause.
2. Check the driver log by passing log_output to the Service to see why it is not responding.
3. Verify the port is not already in use and that localhost loopback is not blocked by firewall/SELinux.
4. Pin a known-good driver/browser version pair if a recent update introduced slow startup.
5. Try a different port explicitly: Service(port=12345).

Example fix

# before — silent hang then failure
service = Service(executable_path='/path/chromedriver')
service.start()  # -> Can not connect to the Service ...

# after — capture logs to diagnose
service = Service(executable_path='/path/chromedriver', log_output='/tmp/driver.log')
service.start()

null

null

from selenium.common.exceptions import WebDriverException
for attempt in range(3):
    try:
        service = Service(executable_path=drv, log_output='/tmp/drv.log')
        service.start()
        break
    except WebDriverException as e:
        if 'Can not connect to the Service' in str(e) and attempt < 2:
            continue
        raise

When it happens

Trigger: The driver binary launched and stays alive but does not open its HTTP port in time: a very slow machine, the driver waiting on a slow DNS/proxy, a port conflict where another process holds the port, or the driver started but is blocked by a firewall from listening on localhost. The is_connectable() check probes utils.is_url_connectable on the chosen port.

Common situations: Under-provisioned CI containers, driver version that hangs on startup (e.g. chromedriver waiting for a browser that is slow to spawn), antivirus/security software intercepting localhost connections, and port exhaustion or NAT issues inside containers.

Related errors

• Service {self._path} unexpectedly exited. Status code was: {
• Service path cannot be None.
• remote server not ready in {} seconds
• SE_MANAGER_PATH does not point to a file: {env_path}
• Unsuccessful command executed: {command}

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/31e2062a7257df20. Report an issue: GitHub.