Chrome DevTools Protocol

CDP: The remote debugging protocol for instrumenting, inspecting, and profiling Chromium-based browsers programmatically.

The Chrome DevTools Protocol (CDP) is the direct communication channel for browser control: it's a remote debugging interface. Tools like Puppeteer and Playwright leverage CDP to instrument, inspect, and debug Chromium and other Blink-based targets. The protocol operates via serialized JSON objects, defining a fixed structure for commands and events across specific domains (e.g., Network, DOM, Debugger). This structured, bidirectional communication enables powerful, high-level automation and deep analysis of the browser's state and behavior.

https://chromedevtools.github.io/devtools-protocol/