Google Chrome team has started initial experimental implementation of Chrome extension manifest V3 in the latest canary builds. The Chrome extension manifest V3 changes were announced more than a year ago now, with intention to add more security, privacy and performance.
The initial manifest v3 proposal was heavily criticized by many leading Chrome extension developers, as several essential and useful APIs were proposed to change. These changes might affect the working of several popular extensions, specially the ad blockers.
The latest canary builds of Chrome have experimental support for manifest v3 changes. The manifest v3 proposed changes are not finalized yet, and several features are currently under work-in-progress stage. Chrome team has also published a migration guide for extension developers, which guides them to migrate to and test new features of manifest v3 proposal.
Few notable proposals of manifest v3 include restriction on remotely hosted code, host permission changes, background service workers (killing background page and scripts), combining page_action and browser_action APIs to single
action API, blocking webRequest API to be replaced with declarativeNetRequest.
Interested developers can refer this migration guide for more information.