1.4WebDriver BiDi: The Standard Catches Up

The W3C did not ignore Playwright's success. In 2023, they began work on WebDriver BiDi (Bidirectional) --- a new protocol that combines WebDriver's standardization with the bidirectional communication model that makes Playwright fast.

WebDriver BiDi uses WebSocket connections instead of HTTP. It supports event subscriptions (the browser can push events to your test, rather than your test polling the browser). It provides richer debugging information. In many ways, it is the W3C acknowledging that Playwright's architectural choices were correct and standardizing them.

As of July 2026, WebDriver BiDi is no longer a future promise --- it is the present. Selenium 4.x exposes low-level BiDi APIs covering roughly 70% of the CDP surface, working in Chrome and Firefox. WebdriverIO v9 uses BiDi as its default protocol. Playwright uses parts of it internally for Firefox and WebKit.

Selenium itself is still on the 4.x line (around 4.41 as of July 2026). Selenium 5 has not shipped --- when it does, its headline feature will be high-level BiDi APIs that wrap today's low-level ones. So the standard is catching up in real, usable increments. But the high-level developer experience --- auto-waiting, browser contexts, the trace viewer --- is still Playwright's advantage. Today, Playwright's custom protocols provide a richer and more reliable experience than what BiDi-based stacks expose.

If you are starting a new project in 2026, use Playwright. If you are maintaining a Selenium codebase, Chapter 18 covers when and how to migrate. If you are evaluating whether to wait for WebDriver BiDi to mature before deciding, do not wait --- the architectural advantages of Playwright are available now.