Manifest V3

Manifest V3 (MV3) is the latest extension platform update, shifting the architecture to enhance security, performance, and user privacy via new API requirements and Service Workers.

MV3 is a major architectural overhaul for browser extensions, specifically targeting security and resource efficiency. The key change is the replacement of Manifest V2's persistent background pages with non-persistent, event-driven Service Workers, which only run when needed, conserving system resources. For network request modification (like in ad blockers), the powerful but privacy-invasive blocking `webRequest` API is deprecated; developers must now use the more restricted, performant `declarativeNetRequest` API, which processes rules natively within the browser. Furthermore, MV3 enforces a strict Content Security Policy (CSP), eliminating support for remotely hosted code to mitigate supply chain attacks, ensuring all code is reviewed and packaged with the extension.

https://developer.chrome.com/docs/extensions/mv3/intro/