[selenium] Can Selenium interact with an existing browser session?

Does anybody know if Selenium (WebDriver preferably) is able to communicate with and act through a browser that is already running before launching a Selenium Client?

I mean if Selenium is able to comunicate with a browser without using the Selenium Server (with could be an Internet Explorer launched manually for example).

This question is related to selenium selenium-webdriver webdriver communication

The answer is


All the solutions so far were lacking of certain functionality. Here is my solution:

public class AttachedWebDriver extends RemoteWebDriver {

    public AttachedWebDriver(URL url, String sessionId) {
        super();
        setSessionId(sessionId);
        setCommandExecutor(new HttpCommandExecutor(url) {
            @Override
            public Response execute(Command command) throws IOException {
                if (command.getName() != "newSession") {
                    return super.execute(command);
                }
                return super.execute(new Command(getSessionId(), "getCapabilities"));
            }
        });
        startSession(new DesiredCapabilities());
    }
}

This is a duplicate answer **Reconnect to a driver in python selenium ** This is applicable on all drivers and for java api.

  1. open a driver
driver = webdriver.Firefox()  #python
  1. extract to session_id and _url from driver object.
url = driver.command_executor._url       #"http://127.0.0.1:60622/hub"
session_id = driver.session_id            #'4e167f26-dc1d-4f51-a207-f761eaf73c31'
  1. Use these two parameter to connect to your driver.
driver = webdriver.Remote(command_executor=url,desired_capabilities={})
driver.close()   # this prevents the dummy browser
driver.session_id = session_id

And you are connected to your driver again.

driver.get("http://www.mrsmart.in")

Inspired by Eric's answer, here is my solution to this problem for selenium 3.7.0. Compared with the solution at http://tarunlalwani.com/post/reusing-existing-browser-session-selenium/, the advantage is that there won't be a blank browser window each time I connect to the existing session.

import warnings

from selenium.common.exceptions import WebDriverException
from selenium.webdriver.remote.errorhandler import ErrorHandler
from selenium.webdriver.remote.file_detector import LocalFileDetector
from selenium.webdriver.remote.mobile import Mobile
from selenium.webdriver.remote.remote_connection import RemoteConnection
from selenium.webdriver.remote.switch_to import SwitchTo
from selenium.webdriver.remote.webdriver import WebDriver


# This webdriver can directly attach to an existing session.
class AttachableWebDriver(WebDriver):
    def __init__(self, command_executor='http://127.0.0.1:4444/wd/hub',
                 desired_capabilities=None, browser_profile=None, proxy=None,
                 keep_alive=False, file_detector=None, session_id=None):
        """
        Create a new driver that will issue commands using the wire protocol.

        :Args:
         - command_executor - Either a string representing URL of the remote server or a custom
             remote_connection.RemoteConnection object. Defaults to 'http://127.0.0.1:4444/wd/hub'.
         - desired_capabilities - A dictionary of capabilities to request when
             starting the browser session. Required parameter.
         - browser_profile - A selenium.webdriver.firefox.firefox_profile.FirefoxProfile object.
             Only used if Firefox is requested. Optional.
         - proxy - A selenium.webdriver.common.proxy.Proxy object. The browser session will
             be started with given proxy settings, if possible. Optional.
         - keep_alive - Whether to configure remote_connection.RemoteConnection to use
             HTTP keep-alive. Defaults to False.
         - file_detector - Pass custom file detector object during instantiation. If None,
             then default LocalFileDetector() will be used.
        """
        if desired_capabilities is None:
            raise WebDriverException("Desired Capabilities can't be None")
        if not isinstance(desired_capabilities, dict):
            raise WebDriverException("Desired Capabilities must be a dictionary")
        if proxy is not None:
            warnings.warn("Please use FirefoxOptions to set proxy",
                          DeprecationWarning)
            proxy.add_to_capabilities(desired_capabilities)
        self.command_executor = command_executor
        if type(self.command_executor) is bytes or isinstance(self.command_executor, str):
            self.command_executor = RemoteConnection(command_executor, keep_alive=keep_alive)

        self.command_executor._commands['GET_SESSION'] = ('GET', '/session/$sessionId')  # added

        self._is_remote = True
        self.session_id = session_id  # added
        self.capabilities = {}
        self.error_handler = ErrorHandler()
        self.start_client()
        if browser_profile is not None:
            warnings.warn("Please use FirefoxOptions to set browser profile",
                          DeprecationWarning)

        if session_id:
            self.connect_to_session(desired_capabilities)  # added
        else:
            self.start_session(desired_capabilities, browser_profile)

        self._switch_to = SwitchTo(self)
        self._mobile = Mobile(self)
        self.file_detector = file_detector or LocalFileDetector()

        self.w3c = True  # added hardcoded

    def connect_to_session(self, desired_capabilities):
        response = self.execute('GET_SESSION', {
            'desiredCapabilities': desired_capabilities,
            'sessionId': self.session_id,
        })
        # self.session_id = response['sessionId']
        self.capabilities = response['value']

To use it:

if use_existing_session:
    browser = AttachableWebDriver(command_executor=('http://%s:4444/wd/hub' % ip),
                                  desired_capabilities=(DesiredCapabilities.INTERNETEXPLORER),
                                  session_id=session_id)
    self.logger.info("Using existing browser with session id {}".format(session_id))
else:
    browser = AttachableWebDriver(command_executor=('http://%s:4444/wd/hub' % ip),
                                  desired_capabilities=(DesiredCapabilities.INTERNETEXPLORER))
    self.logger.info('New session_id  : {}'.format(browser.session_id))

It appears that this feature is not officially supported by selenium. But, Tarun Lalwani has created working Java code to provide the feature. Refer - http://tarunlalwani.com/post/reusing-existing-browser-session-selenium-java/

Here is the working sample code, copied from the above link:

import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.remote.*;
import org.openqa.selenium.remote.http.W3CHttpCommandCodec;
import org.openqa.selenium.remote.http.W3CHttpResponseCodec;

import java.io.IOException;
import java.lang.reflect.Field;
import java.net.URL;
import java.util.Collections;

public class TestClass {
    public static RemoteWebDriver createDriverFromSession(final SessionId sessionId, URL command_executor){
        CommandExecutor executor = new HttpCommandExecutor(command_executor) {

            @Override
            public Response execute(Command command) throws IOException {
                Response response = null;
                if (command.getName() == "newSession") {
                    response = new Response();
                    response.setSessionId(sessionId.toString());
                    response.setStatus(0);
                    response.setValue(Collections.<String, String>emptyMap());

                    try {
                        Field commandCodec = null;
                        commandCodec = this.getClass().getSuperclass().getDeclaredField("commandCodec");
                        commandCodec.setAccessible(true);
                        commandCodec.set(this, new W3CHttpCommandCodec());

                        Field responseCodec = null;
                        responseCodec = this.getClass().getSuperclass().getDeclaredField("responseCodec");
                        responseCodec.setAccessible(true);
                        responseCodec.set(this, new W3CHttpResponseCodec());
                    } catch (NoSuchFieldException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    }

                } else {
                    response = super.execute(command);
                }
                return response;
            }
        };

        return new RemoteWebDriver(executor, new DesiredCapabilities());
    }

    public static void main(String [] args) {

        ChromeDriver driver = new ChromeDriver();
        HttpCommandExecutor executor = (HttpCommandExecutor) driver.getCommandExecutor();
        URL url = executor.getAddressOfRemoteServer();
        SessionId session_id = driver.getSessionId();


        RemoteWebDriver driver2 = createDriverFromSession(session_id, url);
        driver2.get("http://tarunlalwani.com");
    }
}

Your test needs to have a RemoteWebDriver created from an existing browser session. To create that Driver, you only need to know the "session info", i.e. address of the server (local in our case) where the browser is running and the browser session id. To get these details, we can create one browser session with selenium, open the desired page, and then finally run the actual test script.

I don't know if there is a way to get session info for a session which was not created by selenium.

Here is an example of session info:

Address of remote server : http://localhost:24266. The port number is different for each session. Session Id : 534c7b561aacdd6dc319f60fed27d9d6.


It is possible. But you have to hack it a little, there is a code What you have to do is to run stand alone server and "patch" RemoteWebDriver

public class CustomRemoteWebDriver : RemoteWebDriver
{
    public static bool newSession;
    public static string capPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TestFiles", "tmp", "sessionCap");
    public static string sessiodIdPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "TestFiles", "tmp", "sessionid");

    public CustomRemoteWebDriver(Uri remoteAddress) 
        : base(remoteAddress, new DesiredCapabilities())
    {
    }

    protected override Response Execute(DriverCommand driverCommandToExecute, Dictionary<string, object> parameters)
    {
        if (driverCommandToExecute == DriverCommand.NewSession)
        {
            if (!newSession)
            {
                var capText = File.ReadAllText(capPath);
                var sidText = File.ReadAllText(sessiodIdPath);

                var cap = JsonConvert.DeserializeObject<Dictionary<string, object>>(capText);
                return new Response
                {
                    SessionId = sidText,
                    Value = cap
                };
            }
            else
            {
                var response = base.Execute(driverCommandToExecute, parameters);
                var dictionary = (Dictionary<string, object>) response.Value;
                File.WriteAllText(capPath, JsonConvert.SerializeObject(dictionary));
                File.WriteAllText(sessiodIdPath, response.SessionId);
                return response;
            }
        }
        else
        {
            var response = base.Execute(driverCommandToExecute, parameters);
            return response;
        }
    }
}

This snippet successfully allows to reuse existing browser instance yet avoiding raising the duplicate browser. Found at Tarun Lalwani's blog.

from selenium import webdriver
from selenium.webdriver.remote.webdriver import WebDriver

# executor_url = driver.command_executor._url
# session_id = driver.session_id

def attach_to_session(executor_url, session_id):
    original_execute = WebDriver.execute
    def new_command_execute(self, command, params=None):
        if command == "newSession":
            # Mock the response
            return {'success': 0, 'value': None, 'sessionId': session_id}
        else:
            return original_execute(self, command, params)
    # Patch the function before creating the driver object
    WebDriver.execute = new_command_execute
    driver = webdriver.Remote(command_executor=executor_url, desired_capabilities={})
    driver.session_id = session_id
    # Replace the patched function with original function
    WebDriver.execute = original_execute
    return driver

bro = attach_to_session('http://127.0.0.1:64092', '8de24f3bfbec01ba0d82a7946df1d1c3')
bro.get('http://ya.ru/')

This is pretty easy using the JavaScript selenium-webdriver client:

First, make sure you have a WebDriver server running. For example, download ChromeDriver, then run chromedriver --port=9515.

Second, create the driver like this:

var driver = new webdriver.Builder()
   .withCapabilities(webdriver.Capabilities.chrome())
   .usingServer('http://localhost:9515')  // <- this
   .build();

Here's a complete example:

var webdriver = require('selenium-webdriver');

var driver = new webdriver.Builder()
   .withCapabilities(webdriver.Capabilities.chrome())
   .usingServer('http://localhost:9515')
   .build();

driver.get('http://www.google.com');
driver.findElement(webdriver.By.name('q')).sendKeys('webdriver');
driver.findElement(webdriver.By.name('btnG')).click();
driver.getTitle().then(function(title) {
   console.log(title);
 });

driver.quit();

I got a solution in python, I modified the webdriver class bassed on PersistenBrowser class that I found.

https://github.com/axelPalmerin/personal/commit/fabddb38a39f378aa113b0cb8d33391d5f91dca5

replace the webdriver module /usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py

Ej. to use:

from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

runDriver = sys.argv[1]
sessionId = sys.argv[2]

def setBrowser():
    if eval(runDriver):
        webdriver = w.Remote(command_executor='http://localhost:4444/wd/hub',
                     desired_capabilities=DesiredCapabilities.CHROME,
                     )
    else:
        webdriver = w.Remote(command_executor='http://localhost:4444/wd/hub',
                             desired_capabilities=DesiredCapabilities.CHROME,
                             session_id=sessionId)

    url = webdriver.command_executor._url
    session_id = webdriver.session_id
    print url
    print session_id
    return webdriver

Javascript solution:

I have successfully attached to existing browser session using this function

webdriver.WebDriver.attachToSession(executor, session_id);

Documentation can be found here.


I'm using Rails + Cucumber + Selenium Webdriver + PhantomJS, and I've been using a monkey-patched version of Selenium Webdriver, which keeps PhantomJS browser open between test runs. See this blog post: http://blog.sharetribe.com/2014/04/07/faster-cucumber-startup-keep-phantomjs-browser-open-between-tests/

See also my answer to this post: How do I execute a command on already opened browser from a ruby file


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