Why did Selenium 4 move to the W3C WebDriver protocol?

Prior to Selenium 4, WebDriver communicated using the JSON Wire Protocol, a Selenium-project-specific format that predated any official browser vendor standard - meaning every browser vendor had to reverse-engineer or specifically support a Selenium-defined format rather than an independently governed one.

The W3C WebDriver protocol, which Selenium 4 adopted as its default, is instead a formal specification developed with input from browser vendors themselves (Google, Mozilla, Apple, Microsoft), so ChromeDriver, GeckoDriver, and others can implement it as a first-class, natively supported feature rather than an external add-on bolted onto the browser.

This matters practically because it removed a translation/normalization layer that previously existed between the JSON Wire Protocol and each browser's actual native commands, reducing subtle cross-browser inconsistencies and command failures that stemmed from that intermediate translation step rather than from genuine browser differences.