I am able to retrieve the page source when using a standard Chrome browser. Below is my script to achieve this:
from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support.ui import WebDriverWait
chrome_options = Options()
browser = webdriver.Chrome(executable_path="/usr/bin/chromedriver", options=chrome_options)
browser.maximize_window()
wait = WebDriverWait(browser, 40)
url = "https://www.nasdaq.com/market-activity/quotes/nasdaq-ndx-index"
browser.get(url)
wait.until(lambda e: e.execute_script('return document.readyState') != "loading")
print(browser.page_source)
When I run this command:
python3 get_with_head.py
The page opens and I can see all the content. However, after adding three lines to switch to headless mode:
chrome_options.add_argument('--no-sandbox')
chrome_options.add_argument('--disable-dev-shm-usage')
chrome_options.add_argument("--headless")
Here’s my updated script:
from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.support.ui import WebDriverWait
chrome_options = Options()
chrome_options.add_argument('--no-sandbox')
chrome_options.add_argument('--disable-dev-shm-usage')
chrome_options.add_argument("--headless")
browser = webdriver.Chrome(executable_path="/usr/bin/chromedriver", options=chrome_options)
wait = WebDriverWait(browser, 40)
url = "https://www.nasdaq.com/market-activity/quotes/nasdaq-ndx-index"
browser.get(url)
wait.until(lambda e: e.execute_script('return document.readyState') != "loading")
print(browser.page_source)
However, when I execute this script:
python3 get_without_head.py
I get an ‘Access Denied’ message. Why does the content display in normal Chrome but not in headless mode?
Headless browsers can sometimes run into issues where they are detected and blocked by websites that implement bot protection measures. Here are a few strategies you might consider to address the issue:
- User-Agent Modification:
In headless mode, the user-agent of the browser often defaults to something other than what a normal browser would use. Some websites use this to identify bots. You can try setting the user-agent to mimic a standard browser:
chrome_options.add_argument('user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36')
- Additional Headless Options:
Consider adding some of the following options to make the headless browser less detectable:
chrome_options.add_argument('--window-size=1920,1080')
chrome_options.add_argument('--disable-blink-features=AutomationControlled')
- Browser Capabilities:
Adjust the browser capabilities to prevent detection.
desired_capabilities = browser.capabilities
user_agent = desired_capabilities['chrome']['userAgent']
chrome_options.add_argument(f'user-agent={user_agent}')
-
Simulating Behavior:
Add a small delay (use time.sleep) between steps to simulate more realistic human interaction timing. This might help if the website analyzes the speed and timing of requests.
-
JavaScript Execution & Page Visibility API:
Ensure that your script is executing any JavaScript required by the page. Sometimes in headless mode, parts of the page might not load properly:
browser.execute_script('Object.defineProperty(navigator, "webdriver", {get: () => undefined})')
These adjustments help to make the Selenium headless mode behave as close to a full UI browser as possible, reducing the chance of detection and denial. If issues persist, further investigation into specific anti-bot measures on the target website would be necessary.
When using headless mode, sites might detect and block the request due to bot protection measures. To tackle this, try the following:
- User-Agent: Modify it to mimic a regular browser:
chrome_options.add_argument('user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36')
- Window Size: Set a common window size:
chrome_options.add_argument('--window-size=1920,1080')
- Stealth Mode: Modify WebDriver properties:
browser.execute_script('Object.defineProperty(navigator, "webdriver", {get: () => undefined})')
- Disable Automation Detection: Add this option:
chrome_options.add_argument('--disable-blink-features=AutomationControlled')
These adjustments should help reduce detection issues. However, ensure compliance with the site's terms of service.
This issue can indeed arise because headless browsers like Selenium's headless Chrome can be detected and blocked by some websites. Here are some actionable steps to tackle this:
- User-Agent String: Headless browsers usually have a distinct user-agent string that websites can detect. Set the user-agent to mimic a regular browser:
chrome_options.add_argument('user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36')
- Window Size: A non-standard window size might trigger detection. Set it to a common window size:
chrome_options.add_argument('--window-size=1920,1080')
- Stealth Mode: Modify navigator properties to avoid detection:
browser.execute_script('Object.defineProperty(navigator, "webdriver", {get: () => undefined})')
- Realistic Interaction: Implement small delays to mimic human interaction:
import time
time.sleep(2) # Adjust timing as needed
- Disable Automation Features: This disables some browser features that indicate automation:
chrome_options.add_argument('--disable-blink-features=AutomationControlled')
By following these steps, you can reduce the likelihood of your headless browser being detected and improve your ability to access the content. Always consider the target website's terms of service to ensure compliance.
Encountering an 'Access Denied' message when using Selenium's headless mode is a common issue arising from websites implementing bot detection mechanisms. Here are some strategies to mitigate this problem:
- User-Agent String: One of the primary ways websites detect headless browsers is through the user-agent string. By default, headless Chrome presents a user-agent that differs from regular Chrome browsers. You can modify it to resemble a standard browser, which is often less suspicious:
chrome_options.add_argument('user-agent=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36')
- Window Size: Certain websites might flag a non-standard window size. Define a common resolution to avoid being flagged:
chrome_options.add_argument('--window-size=1920,1080')
- Stealth Mode: Disable specific properties that indicate the presence of a headless browser:
browser.execute_script('Object.defineProperty(navigator, "webdriver", {get: () => undefined})')
- Suspension of Automation Features: Disable features that may hint at automation:
chrome_options.add_argument('--disable-blink-features=AutomationControlled')
- Delay Execution: Mimic human behavior by adding delays between actions. This step is crucial to avoid detection based on interaction speed:
import time
# Add a delay to simulate human interaction
time.sleep(2) # Adjust timing as needed
These adjustments can help your headless browser operate more similarly to regular user behavior, reducing detection risks. Always ensure compliance with the website’s terms of service to avoid legal issues.