Google's transition from Manifest V2 to Manifest V3 has been one of the most significant architectural overhauls in the history of browser extension development. For developers building ad blockers, privacy shields, or developer tools, the biggest impact is the deprecation of the blocking capabilities of the chrome.webRequest API.In its place is the chrome.declarativeNetRequest (DNR) API. Instead of letting extensions intercept and inspect network traffic in real-time, the browser now executes filtering on behalf of the extension using declarative rules.