Cannot Start The Driver Service On Http Localhost Selenium Firefox C May 2026

Do not worry. This article will dissect every possible cause of this error—from version hell and path misconfigurations to operating system permissions and port conflicts. By the end, your Firefox automation will start cleanly, every time. Before fixing the problem, you must understand the players involved. Selenium does not control Firefox directly. It uses a separate executable called GeckoDriver . The communication flow looks like this:

from selenium.webdriver.firefox.options import Options options = Options() options.binary_location = r'C:\Program Files\Mozilla Firefox\firefox.exe' # Windows driver = webdriver.Firefox(options=options) Cause 5: The Headless/Background Mode Trap When running Selenium on a headless server (Linux without a GUI, or Docker container), GeckoDriver attempts to create a graphical display. If it fails, the entire service crashes with the localhost error. Do not worry

For Java:

The error occurs only in CI/CD (Jenkins, GitLab CI) but works on your local desktop. Before fixing the problem, you must understand the

from selenium.webdriver.firefox.service import Service service = Service( executable_path='geckodriver.exe', service_args=['--log', 'debug'] # Forces verbose output ) driver = webdriver.Firefox(service=service) The communication flow looks like this: from selenium

from selenium.webdriver.firefox.service import Service service = Service(executable_path='path/to/geckodriver', port=7055) # Classic Selenium port driver = webdriver.Firefox(service=service)