TL;DR: Always use explicit wait. Forget that implicit wait exists.
Here is a quick rundown on the differences between explicit and implicit wait:
- documented and defined behaviour.
- runs in the local part of selenium (in the language of your code).
- works on any condition you can think of.
- returns either success or timeout error.
- can define absence of element as success condition.
- can customize delay between retries and exceptions to ignore.
- undocumented and practically undefined behaviour.
- runs in the remote part of selenium (the part controlling the browser).
- only works on find element(s) methods.
- returns either element found or (after timeout) not found.
- if checking for absence of element must always wait until timeout.
- cannot be customized other than global timeout.
Code examples with explanation. First implicit wait:
WebDriver driver = new FirefoxDriver(); driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS); driver.get("http://somedomain/url_that_delays_loading"); WebElement myDynamicElement = driver.findElement(By.id("myDynamicElement"));
Now explicit wait:
WebDriver driver = new FirefoxDriver(); driver.get("http://somedomain/url_that_delays_loading"); WebDriverWait wait = new WebDriverWait(driver, 10); WebElement myDynamicElement = wait.until( ExpectedConditions.presenceOfElementLocated(By.id("myDynamicElement")));
Both code examples do the same thing. Find a certain element and give up if not found after 10 seconds. The implicit wait can do only this. It can only try to find an element with a timeout. The strength of explicit wait is that it can wait for all kinds of conditions. Also customize timeout and ignore certain exceptions.
Example of possible conditions:
invisibilityOf. Here is a list of the built in expected conditions: https://seleniumhq.github.io/selenium/docs/api/java/org/openqa/selenium/support/ui/ExpectedConditions.html
The implicit wait timeout has effect only on
findElement* methods. If set then all
findElement* will “wait” for the set time before declaring that the element cannot be found.
findElement* will wait is not defined. It depends on browser or operating system or version of selenium. Possible implementations are:
- repeatedly try to find element until timeout. return as soon as element is found.
- try to find element. wait until timeout. try again.
- wait until timeout. try to find element.
This list is gathered from observations and reading bug reports and cursory reading of selenium source code.
My conclusion: Implicit wait is bad. The capabilities are limited. The behaviour is undocumented and implementation dependent.
Explicit wait can do everything implicit wait can and more. The only disadvantage of explicit wait is a bit more verbose code. But that verbosity makes the code explicit. And explicit is better that implicit. Right?
- Official documentation (does not really explain the problematic other than warning from mixing implicit and explicit wait).
- Answer on a related question from Jim Evans. Jim Evans is a maintainer of selenium. Summary: don’t mix implicit and explicit wait.
- Two blog posts explaining implicit and explicit wait in great detail:
- Selected bugs about implicit and explicit wait in selenium:
- What Happens When We Mix Implicit Wait And Explicit Wait
- How to create custom expected conditions in Selenium