AX/GLOSSARY
EngineeringUpdated: Apr 15, 2026

CDP (Chrome DevTools Protocol)

Communication protocol with Chrome / Chromium used by DevTools and all automation tools (Playwright, Puppeteer). WebSocket-based, ~150 methods.

Chrome DevTools Protocol (CDP) is a WebSocket-based protocol used by Chrome DevTools (DevTools in Chromium are written in HTML/CSS/JS and communicate with the browser via CDP) — and by all browser automation tools.

Domains (method categories):

  • Page — navigation, screenshots, lifecycle events
  • DOM — query elements, modify DOM
  • Network — intercept requests, modify responses, throttle
  • Runtime — execute JS, evaluate expressions
  • Input — dispatch mouse/keyboard events
  • Browser — manage browser-level state
  • Storage — cookies, localStorage, IndexedDB
  • Performance — metrics, traces

Total ~150 methods, ~200 events, ~500 types. Largest browser protocol in use.

Practical implications:

  • Playwright and Puppeteer under the hood are wrappers around CDP — you can drop to raw CDP when you need something non-standard
  • Detection by anti-bot: CDP usage has specific signatures (Runtime.evaluate in certain places, specific event sequences)
  • All other Chromium-based browsers (Edge, Brave, Vivaldi, Arc) support CDP
  • Firefox has its own protocol (Marionette), Playwright translates both under one API

Documentation: chromedevtools.github.io/devtools-protocol