The Chrome debugging protocol allows for tools to instrument, inspect, debug and profile Chromium, Chrome and other Blink-based browsers. Many existing projects currently use the protocol. The Chrome DevTools uses this protocol and the team maintains its API.
Consider subscribing to the chrome-debugging-protocol mailing list.
tot: The latest (tip-of-tree) protocol changes frequently and may break at any time. However it captures the full capabilities of the Protocol, whereas the stable release is a subset. There is no backwards compatibility support guaranteed for the capabilities it introduces.
1-2: The 1.2 version of the protocol is the latest stable release of the protocol, tagged at Chrome 54. It includes a smaller subset of the complete protocol compatibilities.