Question: For some tests, I've set up a plain new TrueNAS 12.3 FreeBSD Jail and started it, then installed python3, firefox, geckodriver and pip using the following commands: pkg install python3 firefox geckodriver py38-pip pip install --upgrade pip setenv CRYPTOGRAPHY_DONT_BUILD_RUST 1 pip install cryptography==3.4.7 pip install selenium  Afterwards, when I want to use Selenium with Firefox in my Python code, it does not work: from selenium import webdriver from selenium.webdriver.firefox.options import Options options = Options() options.headless = True driver = webdriver.Firefox(options=options)  it brings Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python3.8/site-packages/selenium/webdriver/firefox/webdriver.py", line 174, in __init__ self.service.start() File "/usr/local/lib/python3.8/site-packages/selenium/webdriver/common/service.py", line 98, in start self.assert_process_still_running() File "/usr/local/lib/python3.8/site-packages/selenium/webdriver/common/service.py", line 110, in assert_process_still_running raise WebDriverException( selenium.common.exceptions.WebDriverException: Message: Service geckodriver unexpectedly exited. Status code was: 64  Funnily, on another Jail that I've set up approximately a year ago (approximately in the mentioned way as well), it just works and does not throw the error (so different versions maybe?)! This is the only content of geckodriver.log: geckodriver: error: Found argument '--websocket-port' which wasn't expected, orisn't valid in this context USAGE: geckodriver [FLAGS] [OPTIONS] For more information try --help  Is there anything I could try to get it working? I've already seen this question, but it seems fairly outdated. Firefox 95.0.2, geckodriver 0.26.0, Python 3.8.12, Selenium 4.1.0

Answer: This error message... selenium.common.exceptions.WebDriverException: Message: Service geckodriver unexpectedly exited. Status code was: 64  and the GeckoDriver log... geckodriver: error: Found argument '--websocket-port' which wasn't expected, or isn't valid in this context  ...implies that the GeckoDriver was unable to initiate/spawn a new Browsing Context i.e. firefox session.  Your main issue is the incompatibility between the version of the binaries you are using as follows:  Your Selenium Client version is 4.1.0. But your GeckoDriver version is 0.26.0.  As @ernstki mentions in their comment:  You are running a geckodriver older than 0.30.0, and it is missing the --websocket-port option, which newer/new-ish versions of Selenium seem to depend on.  To put it in simple words, till the previous GeckoDriver release of v0.29.0 the --websocket-port option wasn't in use, which is now mandatory with Selenium v4.0.1. Further @whimboo also confirmed in his comment:  As it has been manifested the problem here is not geckodriver but Selenium. As such you should create an issue on the Selenium repository instead, so that an option could be added to not always pass the --websocket-port argument. If that request gets denied you will have to use older releases of Selenium if testing with older geckodriver releases is really needed.   Solution Ensure that:  Selenium is upgraded to current levels Version 4.1.0. GeckoDriver is upgraded to GeckoDriver v0.30.0 level. Firefox is upgraded to current Firefox v96.0.2 levels.   FreeBSD versions Incase you are using FreeBSD versions where the GeckoDriver versions are older, in those cases you have to downgrade Selenium to v3.x levels. Commands (courtesy: Kurtibert):  Uninstall Selenium: pip3 uninstall selenium;   Install Selenium: pip3 install 'selenium<4.0.0'