Is Chrome installation needed or only chromedriver when using Selenium?

This error message...

Exception occurred: Failed initializing web driver: Message: unknown error: cannot find Chrome binary  (Driver info: chromedriver=2.40.565498 (ea082db3280dd6843ebfb08a625e3eb905c4f5ab),platform=Windows NT 10.0.14393 x86_64)

...implies that the ChromeDriver was unable to find the Chrome binary while trying to initiate a new new Browsing Context i.e. Chrome Browser session.

As per the documentation with in the wiki page of ChromeDriver:

• ChromeDriver is a standalone server which earlier implemented the WebDriver's wire protocol but slowly and gradually shifting it's implementation as per WebDriver standard.

• The ChromeDriver consists of three separate pieces.

  • There is the browser itself i.e. chrome
  • The language bindings provided by the Selenium project i.e. the driver
  • An executable downloaded from the Chromium project which acts as a bridge between chrome and the driver which is called chromedriver and we refer to it as the server.
• In generic scenarios the server expects you to have Chrome installed in the default location for each system:
  • Linux: /usr/bin/google-chrome ¹
  • Mac: /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome
  • Windows XP: %HOMEPATH%\Local Settings\Application Data\Google\Chrome\Application\chrome.exe
  • Windows Vista and newer: C:\Users\%USERNAME%\AppData\Local\Google\Chrome\Application\chrome.exe

Note: ¹: For Linux systems, the ChromeDriver expects /usr/bin/google-chrome to be a symlink to the actual Chrome binary.

You can find a detailed discussion on overriding the default Chrome binary location in WebDriverException: unknown error: cannot find Chrome binary error with Selenium in Python for older versions of Google Chrome

Solution

So ideally to execute your tests using ChromeDriver / Chrome combo you need to:

• Install the full-blown google-chrome browser.
• Download the compatible version of chromedriver.exe
• Quick installation of ChromeDriver:
  • Mac users with Homebrew: brew tap homebrew/cask && brew cask install chromedriver
  • Debian based Linux distros: sudo apt-get install chromium-chromedriver
  • Windows users with Chocolatey installed: choco install chromedriver
• You can find a couple of relevant discussions in:
  • How to work with a specific version of ChromeDriver while Chrome Browser gets updated automatically through Python selenium
  • Selenium for ChromeDriver and Chrome Browser and the log message “Only local connections are allowed”
  • WebDriverException: Message: Service /usr/lib/chromium-browser/chromedriver unexpectedly exited on Raspberry-Pi with ChromeDriver and Selenium

Reference

You can find a detailed discussion in:

• WebDriverException: unknown error: cannot find Chrome binary error with Selenium in Python for older versions of Google Chrome

Users provided relevant link to confirm that, "YES" a full Chrome installation is needed in addition to the actual chromedriver.

Link: https://github.com/SeleniumHQ/selenium/wiki/ChromeDriver