Can a website detect when you are using selenium with chromedriver?

I've been testing out Selenium with Chromedriver and I noticed that some pages can detect that you're using Selenium even though there's no automation at all. Even when I'm just browsing manually just using chrome through Selenium and Xephyr I often get a page saying that suspicious activity was detected. I've checked my user agent, and my browser fingerprint, and they are all exactly identical to the normal chrome browser.

When I browse to these sites in normal chrome everything works fine, but the moment I use Selenium I'm detected.

In theory chromedriver and chrome should look literally exactly the same to any webserver, but somehow they can detect it.

If you want some testcode try out this:

    from pyvirtualdisplay import Display
    from selenium import webdriver

    display = Display(visible=1, size=(1600, 902))
    chrome_options = webdriver.ChromeOptions()
    driver = webdriver.Chrome(chrome_options=chrome_options)
    print 'arguments done'

If you browse around stubhub you'll get redirected and 'blocked' within one or two requests. I've been investigating this and I can't figure out how they can tell that a user is using Selenium.

How do they do it?


I installed the Selenium IDE plugin in Firefox and I got banned when I went to in the normal firefox browser with only the additional plugin.


When I use Fiddler to view the HTTP requests being sent back and forth I've noticed that the 'fake browser\'s' requests often have 'no-cache' in the response header.


results like this Is there a way to detect that I'm in a Selenium Webdriver page from Javascript suggest that there should be no way to detect when you are using a webdriver. But this evidence suggests otherwise.


The site uploads a fingerprint to their servers, but I checked and the fingerprint of selenium is identical to the fingerprint when using chrome.


This is one of the fingerprint payloads that they send to their servers


Its identical in selenium and in chrome


VPNs work for a single use but get detected after I load the first page. Clearly some javascript is being run to detect Selenium.

For Mac Users

Replacing`cdc` variable using Vim or Perl_

You can use vim, or as @Vic Seedoubleyew has pointed out in the answer by @Erti-Chris Eelmaa, perl, to replace the cdc_ variable in chromedriver( See post by @Erti-Chris Eelmaa to learn more about that variable ). Using vim or perl prevents you from having to recompile source code or use a hex-editor. Make sure to make a copy of the original chromedriver before attempting to edit it. Also, the methods below were tested on chromedriver version 2.41.578706.

Using Vim

    vim /path/to/chromedriver

After running the line above, you'll probably see a bunch of gibberish. Do the following:

  1. Search for cdc_ by typing /cdc_ and pressing return.
  2. Enable editing by pressing a.
  3. Delete any amount of $cdc_lasutopfhvcZLmcfl and replace what was deleted with an equal amount characters. If you don't, chromedriver will fail.
  4. After you're done editing, press esc.
  5. To save the changes and quit, type :wq! and press return.
  6. If you don't want to save the changes, but you want to quit, type :q! and press return.
  7. You're done.

Go to the altered chromedriver and double click on it. A terminal window should open up. If you don't see killed in the output, you successfully altered the driver.

Using Perl

The line below replaces cdc_ with dog_:

    perl -pi -e 's/cdc_/dog_/g' /path/to/chromedriver

Make sure that the replacement string has the same number of characters as the search string, otherwise the chromedriver will fail.

Perl Explanation

s///g denotes that you want to search for a string and replace it globally with another string (replaces all occurrences).

e.g., s/string/replacment/g


s/// denotes searching for and replacing a string.

cdc_ is the search string.

dog_ is the replacement string.

g is the global key, which replaces every occurrence of the string.

How to check if the Perl replacement worked

The following line will print every occurrence of the search string cdc_:

perl -ne 'while(/cdc_/g){print "$&\n";}' /path/to/chromedriver

If this returns nothing, then cdc_ has been replaced.

Conversely, you can use the this:

perl -ne 'while(/dog_/g){print "$&\n";}' /path/to/chromedriver

to see if your replacement string, dog_, is now in the chromedriver binary. If it is, the replacement string will be printed to the console.

Go to the altered chromedriver and double click on it. A terminal window should open up. If you don't see killed in the output, you successfully altered the driver.

Wrapping Up

After altering the chromedriver binary, make sure that the name of the altered chromedriver binary is chromedriver, and that the original binary is either moved from its original location or renamed.

My Experience With This Method

I was previously being detected on a website while trying to log in, but after replacing cdc_ with an equal sized string, I was able to log in. Like others have said though, if you've already been detected, you might get blocked for a plethora of other reasons even after using this method. So you may have to try accessing the site that was detecting you using a VPN, different network, or what have you.