Selenium “Unable to find a matching set of capabilities” despite driver being in /usr/local/bin

1.1K    Asked by HienCastanon in QA Testing , Asked on Jul 15, 2021

I'm trying to follow a tutorial about Selenium, I've downloaded the latest version of the geckodriver and copied it to /usr/local/bin. However, when I try

from selenium import webdriver
driver = webdriver.Firefox()
I get the following error message:
Traceback (most recent call last):
  File "/Users/kurtpeek/Documents/Scratch/", line 4, in
    driver = webdriver.Firefox()
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/selenium/webdriver/firefox/", line 152, in __init__
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/selenium/webdriver/remote/", line 98, in __init__
    self.start_session(desired_capabilities, browser_profile)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/selenium/webdriver/remote/", line 188, in start_session
    response = self.execute(Command.NEW_SESSION, parameters)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/selenium/webdriver/remote/", line 252, in execute
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/selenium/webdriver/remote/", line 194, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.WebDriverException: Message: Unable to find a matching set of capabilities
[Finished in 1.2s with exit code 1]

From, it seems like other users are experiencing similar issues, but the Selenium team is unable to reproduce it. How can I get Selenium working with Firefox? (It does work with chromedriver and a webdriver.Chrome() instance, so I suspect this might be a bug in Selenium).

Answered by Gordon Guess

To resolve unable to find a matching set of capabilities you can use the below mentioned code. In my case, I have updated Firefox and Selenium.

Updated Firefox 48 → 53

Updated to Selenium 3.4.1

I also used Homebrew to reinstall/update Geckodriver and explicitly use it as an executable for Selenium WebDriver, but it turned out that it wasn't necessary to mitigate the "Unable to find a matching set of capabilities" error.

Also, check whether you have the correct version 32/64bit for your geckodriver or not.

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