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

Updating Firefox and Selenium solved it for me. I don't pretend to have an explanation for the root cause however.

• Updated Firefox 48 → 53
• Updated to Selenium 3.4.1

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

I had this same issue, and the problem was related to using Firefox ESR (I'm on Debian). To be more specific, I'm on Debian 10 using 64-bit Firefox 68.11.0esr, python3.7, selenium 3.141.0, and geckodriver 0.27.0.

Here's the standard example I used that failed:

from selenium import webdriver

browser = webdriver.Firefox()
browser.get("http://google.com")

As recommended in this answer, I changed:

browser = webdriver.Firefox()

to

browser = webdriver.Firefox(firefox_binary="/usr/bin/firefox-esr")

and it worked.

If you don't know the path to firefox-esr, you can run sudo find / -name firefox-esr on the command line. Several should come up.

for me it was enough to just upgrade FF