selenium - What is the difference between WebDriver and DevTool protocol

Question

As we known WebDriver protocol is design for automation test purpose. But the major browsers also provide DevTool protocol. In some cases the DevTool protocol could achieve more powerful interactions and operations compare to WebDriver.

My question is why there are two different protocols and what's the main difference between these two protocols? Is there any selection experience available to share for a project development?

Thanks in advance!

Reference:

• DevTools

  • https://docs.microsoft.com/en-us/microsoft-edge/devtools-protocol/
  • https://chromedevtools.github.io/devtools-protocol/
  • https://searchfox.org/mozillacentral/source/devtools/docs/backend/protocol.md

• WebDriver:

  • https://www.seleniumhq.org/projects/webdriver/
  • https://www.w3.org/TR/webdriver1/
  • https://docs.microsoft.com/en-us/microsoft-edge/webdriver
  • https://developer.mozilla.org/en-US/docs/Mozilla/QA/Marionette/WebDriver
  • https://sites.google.com/a/chromium.org/chromedriver/downloads

Answer 1

Main difference between WebDriver protocol and DevTools protocol is that WebDriver protocol needs a middle man like browser-driver (eg: chrome-driver) which is a server that sits between the automation script and browser enabling browser control, but in case of DevTools protocol the automation script can directly talk to browser running in debug mode making headless automation pretty straight forward.

And Chrome driver internally uses DevTools protocol to control browser, so if we are using WebDriver protocol it will in turn use Devtools protocol to control browser.

If cross-browser testing is something important for the new testing tool, DevTools protocol may not be suitable now, as there is no standard yet and it is mostly work in progress. Otherwise DevTools protocol will be a great choice as it gives more control like intercepting request header, simulating network etc and makes headless automation way easier.