How to change the User Agent AT and BEFORE Runtime using Selenium in Python

Change or even Rotate the User Agent using Selenium for Chrome and Firefox using following code :)

CONTENTS
  1. Before Runtime
    2.
  2. At Runtime
    3.
Louis Klimek
Louis Klimek

Before Runtime

Setting a User Agent BEFORE RUNTIME is pretty straight forward using WebDriver Options / WebDriver Profiles that are available for Chrome (ChromeDriver) / Firefox (GeckoDriver).

You can invoke Google Chrome with a user agent using the command line and following command without even using Selenium: chrome --user-agent=Whatever

But if you want to use this with selenium you can give the same Arguments using the following Python Code for Google Chrome:

from selenium import webdriver
from selenium.webdriver.common.by import By

#Change Browser Options
option = webdriver.ChromeOptions()
option.add_argument("user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36")

#Open Browser
browser = webdriver.Chrome(executable_path='chromedriver.exe', options=option)

Firefox has a variable called general.useragent.override in your Firefox Profile.

You can make Selenium use a profile different from the default one and edit that with your new User Agent, using this Python Code:

from selenium import webdriver

#Change Profile
profile = webdriver.FirefoxProfile()
profile.set_preference("general.useragent.override", "whatever you want")

#Open Browser
browser = webdriver.Firefox(profile)

At Runtime

As far as I know, you can only change your User Agent during runtime with Chrome because when you configure a GeckoDriver instance (Firefox) to start a new Firefox Browser Session, Firefox's configuration remains unchanged during the lifetime of the Firefox instance and remains unmodifiable.

But using the execute_cdp_cmd(cmd, cmd_args) command for Chrome you can easily execute google-chrome-devtools commands with Selenium - such as easily changing the user agent AT RUNTIME, for instance - or even changing your User Agent between each request without needing to restart.

See following Python Code:

from selenium import webdriver

driver = webdriver.Chrome(executable_path='chromedriver.exe')

#Print original User Agent
print(driver.execute_script("return navigator.userAgent;"))

# Set and print First Custom User Agent
driver.execute_cdp_cmd('Network.setUserAgentOverride', {"userAgent": 'YOUR FIRST USER AGENT HERE'})
print(driver.execute_script("return navigator.userAgent;"))

# Set and print Second Custom User Agent
driver.execute_cdp_cmd('Network.setUserAgentOverride', {"userAgent": 'YOUR SECOND USER AGENT HERE'})
print(driver.execute_script("return navigator.userAgent;"))

# Open httbin.org to see current user agent in Browser
driver.get('https://www.httpbin.org/headers')