selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities with Firefox 46 through Selenium

Question

I must have some versions here that don't match up since I can't get Selenium with Python to fire up a Firefox web browser. I'm using an older version of Firefox because other people in here have the same old version of Python and for them the old version of Firefox works best.

Code:

from selenium import webdriver
from selenium import common
from selenium.webdriver import ActionChains
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException
from selenium.common.exceptions import NoSuchElementException
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
driver=webdriver.Firefox(capabilities=DesiredCapabilities.FIREFOX)

Error:

Traceback (most recent call last):
 File "scrapeCommunitySelenium.py", line 13, in <module>
 driver=webdriver.Firefox(capabilities=DesiredCapabilities.FIREFOX)
 File "/Library/Python/2.7/site-packages/selenium/webdriver/firefox/webdriver.py", line 158, in __init__
 keep_alive=True)
 File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 154, in __init__
 self.start_session(desired_capabilities, browser_profile)
 File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 243, in start_session
 response = self.execute(Command.NEW_SESSION, parameters)
 File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 311, in execute
 self.error_handler.check_response(response)
 File "/Library/Python/2.7/site-packages/selenium/webdriver/remote/errorhandler.py", line 237, in check_response
 raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities

Version info:

• Python 2.7.10
• Selenium 3.8.0
• Firefox 46.0
• GeckoDriver 0.19.1 (It's in a folder which is in my PATH environment variable)
• MacOS 10.12.6

• Eugene S: Are running that on Grid or locally?
• Eamonn Gormley: Running it locally.

Answer 1

As you are using Selenium 3.8.0 you have to use GeckoDriver as a mandatory. But again as you are using Firefox v46.0 you have to set the capability marionette as False through DesiredCapabilities() as follows :

from selenium import webdriver
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities
cap = DesiredCapabilities().FIREFOX
cap["marionette"] = False
browser = webdriver.Firefox(capabilities=cap, executable_path="C:\\path\\to\\geckodriver.exe")
browser.get('http://google.com/')
browser.quit()

• akshay dhule: ' cap["marionette"] = false ' => gives error : 'caps not defined'. What does this line change?
• FilBot3: I keep getting "The browser appears to have exited before we could reconnect." However, its asking to close the browser each time I run the thing.
• Darsh Patel: This solution also works for MacOS, just need to change the executable path.

Answer 2

If you're going to use Geckodriver, you definitely need to use a newer version of Firefox. Frex: https://github.com/mozilla/geckodriver/releases/tag/v0.19.0 lists FF55 or greater.

If you plan on using FF46, don't use geckodriver. Update your capabilities to have marionette set to False:

caps = DesiredCapabilities.FIREFOX.copy()
caps['marionette'] = False
driver=webdriver.Firefox(capabilities=caps)

• Eamonn Gormley: Setting marionette to False seems to do the trick. Thank you!

Answer 3

I had this issue on my MacOS 10.5 Catalina. What I did: 1. Installed the geckodriver using brew install geckodriver 2. Deleted/uninstalled my existing(OLD) Firefox browser (v.46) and installed v70. 3. tried:

from selenium import webdriver
browser = webdriver.Firefox()
browser.get('http://google.com')

The above worked fine with no errors, by launching Firefox and loading google.com

Answer 4

I got this error because the Firefox browser was not installed on my machine. You can download Firefox or download the Chrome driver here. If you use the Chrome drive, make sure you add it to the path (just like the geckodriver).

And the you can use it like this:

from selenium import webdriver
driver = webdriver.Chrome()
driver.get("http://www.python.org")

• Yaakov Bressler: SAME here! Wow, I must've read over 75 webpages before coming across this...

Answer 5

You can see similar error on Chrome as well. If you are seeing it on Ubuntu, the reason is probably you have a pre-installed version of Chrome and Firefox which is older. And you have downloaded the latest version of Chrome/Firefox driver.

Simple solution is:

1. Uninstall the existing Chrome/Firefox browser provided from Ubuntu : Go to Applications(top left corner)->Ubuntu software center-> search Chrome and uninstall it.
2. Install latest browser.

For Chrome, steps are as follows:

1. wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb

2. sudo dpkg -i google-chrome-stable_current_amd64.deb

Done!

Answer 6

There are some possible reasons for that error like:

1. Firefox is installed in your system
2. Firefox access is admin only
3. Firefox is not installed with same name
4. Firefox version is not updated

Answer 7

This error can also come from the version 32bits, choose a x64 version to fix it.