Types of Selenium exceptions
Selenium exceptions root causes

1. NoSuchElementException
WebDriver is not able to find the existence of web element on the web page.
Here, the FindElementBy method is unable to find the web element.

Root Cause:
Elements are removed from the DOM
Xpath you specified for the element may be wrong
AJAX has not returned yet and you've already obtain NoSuchElementException
Page is still being rendered but you've already finished your element search because of low wait time
The element is not on the page at all

2. NoSuchWindowException
Selenium WebDriver is unable to switch to the window.

Root Cause:
Current window closed
Target window is not opened yet, but you were trying to perform operation
When target window has been closed but still the code tried to perform operation on the target window.

3. NoSuchFrameException
WebDriver is unable to switch to the given frame.

Root Cause:
Invalid name of the frame
Switchable frame does not exist
We have not given enough wait time to load the frame

4. NoAlertPresentException
Selenium WebDriver is unable to switch to the alert.
Here Alert popup could be Alert Box, Confirmation Box, Prompt Box from the Javascript commands.

Root Cause:
When user tries to access alert which is not present in the at current time
When javascript alert is blocked in the browser
Not giving enough time for the alert to load
When alert is already closed

5. ElementNotSelectableException
WebDriver is not able to select or click the web element on Application under test (AUT).

Root Cause:
The attribute of the web element is set to disable

6. ElementNotVisibleException
This type of Exception occurs when existing element in DOM has an attribute set as hidden.
In this case, elements are there, but they are not visible or available to interact with the WebDriver.

Root Cause:
HTML element’s attribute set to ‘hidden’
Trying to use sendkeys to element which is not visible

7. ElementNotSelectableException
This exception is thrown when an element is present in the DOM but not able to select.

Root Cause:
Element may be overlapped by another element.

8. InvalidSelectorException
When you write wrong XPath syntax then this exception may occur.

Root Cause:
XPath syntax is not correct

9. TimeoutException
This exception occurs when we use wait commands like Implicit Wait, Explicit Wait or Fluent Wait.
Once any of the waits fails after exceeding defined time then TimeoutException occurs.

Root Cause:
WebDriver fails to perform an activity in defined time within Implicit Wait or Explicit Wait

10. WebDriverException
This exception occurs when the WebDriver is performing the action right after you close the browser.

Root Cause:
WebDriver trying to execute a statement after the browser is closed.

11. StaleElementReferenceException
This exception occurs when the web element gets detached from the current DOM.

Root Cause:
JavaScript or JS library has deleted an element and replaced it with one with the same ID or attributes.

12. ScreenshotException
This will be thrown when selenium fails to take screenshot of the webpage.
If ScreenshotException occurs then the screenshot captured turns black

Root Cause:
When we try to take screenshot in headless browser(phantomjs, htmlunitdriver) without enabling the screenshot functionality

13. ScriptTimeoutException 
Webdriver throws ScriptTimeoutException exception when executeAsyncScript takes more time than given time limit to return the value.

Root Cause:
Webpage running a long running script

14. InsecureCertificateException 
Navigation made the user agent to hit a certificate warning, which is caused by an invalid or expired TLS certificate.

Root Cause:
Website is does not has valid certificate

15. UnableToSetCookieException 
This exception is thrown when a driver fails to set a cookie.

Root Cause:
You are trying to set the cookie without specifying the domain

Possible Interview Questions on selenium exceptions:
What are the different Selenium exception?
What is NoSuchElementException and what are its root causes?
What is NoSuchWindowException and what are its root causes?
What is NoSuchFrameException and what are its root causes?
What is NoAlertPresentException and what are its root causes?
What is ElementNotSelectableException and what are its root causes?
What is ElementNotVisibleException and what are its root causes?
What is ElementNotSelectableException and what are its root causes?
What is InvalidSelectorException and what are its root causes?
What is TimeoutException and what are its root causes?
What is WebDriverException and what are its root causes?
What is StaleElementReferenceException and what are its root causes?
What is ScreenshotException and what are its root causes?
What is ScriptTimeoutException and what are its root causes?
What is InsecureCertificateException and what are its root causes?
What is UnableToSetCookieException and what are its root causes?

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