How to Make Firefox Headless Programmatically in Selenium with Python

How to make Firefox headless programmatically in Selenium with Python?

To invoke Firefox Browser headlessly, you can set the headless property through Options() class as follows:

from selenium import webdriver
from selenium.webdriver.firefox.options import Options

options = Options()
options.headless = True
driver = webdriver.Firefox(options=options, executable_path=r'C:\Utility\BrowserDrivers\geckodriver.exe')
driver.get("http://google.com/")
print ("Headless Firefox Initialized")
driver.quit()

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There's another way to accomplish headless mode. If you need to disable or enable the headless mode in Firefox, without changing the code, you can set the environment variable MOZ_HEADLESS to whatever if you want Firefox to run headless, or don't set it at all.

This is very useful when you are using for example continuous integration and you want to run the functional tests in the server but still be able to run the tests in normal mode in your PC.

$ MOZ_HEADLESS=1 python manage.py test # testing example in Django with headless Firefox

or

$ export MOZ_HEADLESS=1   # this way you only have to set it once
$ python manage.py test functional/tests/directory
$ unset MOZ_HEADLESS      # if you want to disable headless mode

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Steps through YouTube Video

• Mozilla Firefox in Headless Mode through Selenium 3.5.2 (Java)
• Login into Gmail Account using Headless Chrome through Selenium Java

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Outro

How to configure ChromeDriver to initiate Chrome browser in Headless mode through Selenium?

Selenium Firefox headless returns different results

Ideally, using and not using firefox_options.headless = True shouldn't have any major effect on the elements within the DOM Tree getting rendered but may have a significant difference as far as the Viewport is concerned.

As an example, when GeckoDriver/Firefox is initialized along with the --headless option the default Viewport is width = 1366px, height = 768px where as when GeckoDriver/Firefox is initialized without the --headless option the default Viewport is width = 1382px, height = 744px.

• Example Code:

  from selenium import webdriver
  from selenium.webdriver.support.ui import WebDriverWait
  from selenium.webdriver.common.by import By
  from selenium.webdriver.support import expected_conditions as EC
  
  options = webdriver.FirefoxOptions()
  options.headless = True
  driver = webdriver.Firefox(options=options, executable_path=r'C:\Utility\BrowserDrivers\geckodriver.exe')
  driver.get("https://www.google.com/")
  WebDriverWait(driver, 10).until(EC.element_to_be_clickable((By.NAME, "q")))
  print ("Headless Firefox Initialized")
  size = driver.get_window_size()
  print("Window size: width = {}px, height = {}px".format(size["width"], size["height"]))
  driver.quit()
  driver = webdriver.Firefox(executable_path=r'C:\Utility\BrowserDrivers\geckodriver.exe')
  driver.get("https://www.google.com/")
  WebDriverWait(driver, 10).until(EC.element_to_be_clickable((By.NAME, "q")))
  print ("Firefox Initialized")
  size = driver.get_window_size()
  print("Window size: width = {}px, height = {}px".format(size["width"], size["height"]))
  driver.quit()
  

• Console Output:

  Headless Firefox Initialized
  Window size: width = 1366px, height = 768px
  Firefox Initialized
  Window size: width = 1382px, height = 744px
  

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Conclusion

From the above observation it can be inferred that with --headless option GeckoDriver/Firefox opens the Browsing Context with reduced Viewport and hence the number of elements identified can be less.

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Solution

While using GeckoDriver/Firefox to initiate a Browsing Context always open in maximized mode or configure through set_window_size() as follows:

from selenium import webdriver
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.common.by import By
from selenium.webdriver.support import expected_conditions as EC

options = webdriver.FirefoxOptions()
options.headless = True
#options.add_argument("start-maximized")
options.add_argument("window-size=1400,600")
driver = webdriver.Firefox(options=options, executable_path=r'C:\Utility\BrowserDrivers\geckodriver.exe')
driver.get("https://www.google.com/")
driver.set_window_size(1920, 1080)

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tl; dr

You find a couple of relevant discussion on window size in:

• python: How to set window size in Selenium Chrome Python
• java: Not able to maximize Chrome Window in headless mode

Python Selenium Firefox - how to enable headless-mode as part of a class/object?

Please try following code :

options = Options()
options.add_argument("--headless")
driver = webdriver.Firefox(firefox_options=options)

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