WebDriver Architecture

All implementations of WebDriver that communicate with the browser, or a RemoteWebDriver server use a common wire protocol. This wire protocol defines a RESTful web service using JSON over HTTP.

So each WebDriver command is mapped to an HTTP method via the WebDriver service, and then passed on to the HTTP Command Processor to communicate with the browser. The Command responses are returned as HTTP/1.1 response messages via the WebDriver service.

Different drivers, such as the Firefox Driver and the IE Driver, have different implementations to accomplish the above.

The Selenium WebDriver architecture document linked below goes into further details on how these are implemented and how WebDrvier commands flow through to the browser and back. Read section 16.6 for details on the Firefox Driver.

Execution Flow:

Step 1. Automation Script is written using Client binding for different languages

Step 2. Once Test execution is started

Step 3. Browser driver is created

Step 3. Respective Driver.exe file starts “HTTP server” and starts listening for HTTP requests.

Step 4. A new HTTP request Creates, as each Selenium Method contains is mapped to respected webDriver API

Step 5. HTTP request is sent to the HTTP server

Step 6. HTTP server determines the steps needed for implementing the Selenium command

Step 7. The implementation steps are sent to the browser

Step 8. The HTTP server send the execution status back to the test script