What is Selenium? Does it support multiple users?

Selenium is a programming tool used to automate the browser — simulating a real user by opening windows, going to URLs, clicking buttons, filling in forms, etc. Selenium is primarily used for test automation, but can also be used for other things.

Selenium is available as a library for most popular programming languages, including Java, JavaScript, TypeScript, C#, Python, Ruby, PHP, etc.

It is also referred to as Selenium WebDriver, because there were two different projects (Selenium & WebDriver) which did similar things and eventually merged. Selenium uses the WebDriver protocol (a W3C standard now) to communicate over the network via a REST API. This allows for remote automation,

There are other tools associated with Selenium, including Selenium Grid — which enables remote execution of automation and Selenium IDE — which allows you to record and play back automated steps without writing code, and has (limited) ability to to export from Selenium IDE to code that can run independent.

Selenium IDE does not support multiple users, but scripts can be exported and shared from one user to another.

Selenium Grid allows for parallel remote execution of Selenium scripts, which allows multiple people (or tests) to execute tests at the same time.

The concept of “supporting multiple users” does not really make sense in terms of Selenium as an open source development tool or coding library.

It would be like saying:
“Does Microsoft Word support multiple users?” or
“Does the Java programming language support multiple users?”

In the case of Microsoft Word, every user that has the program can use it, but collaboration is (primarily) done outside of the tool. With proprietary software like Microsoft Word, each user may need a license to run their own copy of the application, but Selenium is open source, so does not require the purchase of any license to use.

And as a programming library, any number of users can reference Selenium in their own code and execute it. Users can run multiple automated tests (or other scripts) at once — if they write their program to run in parallel.

But in order to maximize parallel execution (for single or multiple users) you need to have a remote Selenium grid. There is an open source grid that anyone can deploy, but there are also commercial services the host Selenium Grid with additional tools at a cost. These companies include Sauce Labs, BrowserStack, LambdaTest, and Applitools. Each company has their own policy about multiple users, and of the ones I mentioned, they all support multiple users in their own way.

This post is based on a question asked on Quora at: https://www.quora.com/What-is-Selenium-Does-it-support-multiple-users

How long does it take to learn Selenium and Python

This is another post that grew out of a question asked by someone else online.

Here is the original question (and my answer) on Quora:


There are several different things here, and they affect how long it will take you to learn Selenium with Python.

Let’s break it down:

  1. Learning Selenium
  2. Learning Python
  3. Learning programming
  4. Learning test automation

Your existing knowledge in each of these topics will affect how easy it is.

For example, if you’ve already used Selenium with another programming language, that means that (to some degree) you also know programming and test automation principles. So all you need to learn is Python.

But if you have some programming experience in JavaScript but have never done test automation (with or without Selenium) or used Python, you come with general programming knowledge (but using a different paradigm) there are more obstacles.

Alternately, you may have experience with test automation so you understand the goals, but have used a commercial low-code record and playback automation tool. This may actually be harder than starting from a programming background because it requires a paradigm shift in your strategy to test automation.

However, probably most people asking this question have some experience manually testing software, a basic knowledge of programming (either in Python, or some other language — but would not consider themselves expert), and want to know how long it would take them to become competent enough with Selenium and Python to either:

A. Get a job doing test automation with Selenium and Python or
B. Apply test automation with Selenium and Python in their current job
(which may be manual testing, or some other role).

So, I’ll try to answer this question.

Give yourself a few weeks to learn the basics of Python, general programming principles, and the “Pythonic” idioms. A good course on Udemy or book about Python is about what you need. Subtract if you already understand some of this, if you’re a fast learner, or have guidance (such as a mentor.)

But it’s not really about how quickly you can absorb knowledge, it’s practice to retain it, and having the time to make mistakes and experiment.

And then it will only take a week or two to pick up Selenium. It has a fairly straightforward API, and the concepts of automating finding buttons and clicking on them is fairly simple to understand. There are some obstacles that can trip you up though — things like provisioning and configuring a WebDriver, managing sessions, “getting” locators like XPath and CSS, data driven, using Pytest and fixtures, etc can trip you up and lead to hours (or days) of frustration — or you can establish bad habits that will bite you in the future.

But applying Selenium in a meaningful way to write useful test automation may take additional weeks, or months (or years) of practice. Again, this depends on your personal curiosity, cleverness, mentoring opportunities, and above all, practice and ability to apply it in the real world.

These challenges fall under writing good maintainable test automation, knowing what to test and how to approach it, and even little things like picking good locators, or naming functions and variables well.

If you were smart, and scrolled to the bottom, short answer is:

It should only take you a few weeks to pick up Python and Selenium, depending on where you are coming from experience-wise and how fast you learn. Having mentors and or guided learning can help you focus on what’s important and get past silly obstacles. But like anything, it will take a much longer time to master, and depend on real world experience applying the principles, making mistakes, and learning from them.

A reasonable time to go from basic programming knowledge and no test automation experience to competent enough to make an impact at a job (e.g. get hired as a junior test automation engineer) is a few months of steady learning and practice.

When should you use JavaScriptExecutor in Selenium?

When you want to execute JavaScript on the browser :)

This was my answer to a question on Quora


JavaScriptExecutor is an interface that defines 2 methods:

in Java (and similarly in C#):

Object executeScript(String script, Object... args)


Object executeAsyncScript(String script, Object... args)

which take as an argument a string representing the JavaScript code you want to execute on the browser and (optionally) one or more arguments. If the second argument is a WebElement it will apply the script to the corresponding HTML element. Arguments are added to the JS magic arguments variable which represents the values passed to a function. If the code executed returns a value, that is returned to your Selenium code

Each driver is responsible for implementing it for the browser.

RemoteWebDriver implements it as well.

But when *you* as a Selenium user want to use JavaScriptExecutor is when you assign a driver to the base type WebDriver, which does not implement it.

in this case, you cast your driver instance (which really does implement executeScript() and executeScriptAsync().

For example

WebDriver driver = new ChromeDriver();  

// base type ‘WebDriver’ does not define executeScript() although our instance that extends RemoteWebDriver actually does implement it.

// So we need to cast it to ‘JavaScriptExecutor’ to let the Java compiler know.

JavaScriptExecutor js = (JavaScriptExecutor) driver;

js.executeScript(“alert(‘hi from Selenium’);”

if you keep your instance typing, you do not need to cast to JavaScriptExecutor.

RemoteWebDriver driver = new RemoteWebDriver(url, capabilities);  

// information about our type is not lost so the Java compiler knows our object implements executeScript()

WebElement element = driver.findElement(By.id(“mybutton”));

driver.executeScript(“arguments[0].click();", element);

// in the above case it adds the element to arguments and performs a click() event (in JavaScript in the browser) on our element

String htmlsnippet = driver.executeScript(“return document.querySelector(‘#myid’).outerHTML” , element);

// this time we use native JavaScript on the browser to find an element and return its HTML, bypassing Selenium’s ability to do so.

The above two examples illustrate ways you can accomplish in JavaScript what you would normally use Selenium for.

Why would you do this?

Well, sometimes the driver has a bug, or it can be more efficient (or reliable) to do in JavaScript, or you might want to combine multiple actions in 1 WebDriver call.

Weekly Wednesday Webinar on Selenium & Sauce Labs

I’ve been working at Sauce Labs for a while now, helping enterprise users build test automation frameworks and implement continuous integration using Selenium & Sauce Labs.

In order to reach a larger audience — and to learn more about people’s challenges developing test automation — I’m going to be hosting a weekly webinar on using Selenium with Sauce Labs for test automation.

So, starting this week, each Wednesday during lunch (12:30pm Mountain Time) I’ll host a webinar / office hours.  I’ll begin with a brief presentation introducing the topic, followed by a demo (live coding — what could go wrong?), and then open it up for questions & comments.

The first webinar will be tomorrow at 12:30pm MST.  The topic is DesiredCapabilities.

I’ll talk about what desired capabilities are, how to use desired capabilities with Sauce Labs, and show how you can use the  Sauce Labs platform configurator to generate desired capabilities.  I’ll also talk about Sauce Labs specific capabilities used to report on tests and builds.

Register on EventBrite here: Selenium & Sauce Labs Webinar: Desired Capabilities

Join the WebEx directly: Selenium & Sauce Labs Webinar: Desired Capabilities

Contact me if you’d like a calendar invite or more info.