An integer specifying the version of the manifest file format your package requires. This key is required. For example:
Supported values for this key are:
3: Use the Manifest V3 format and associated feature set.
The current version is Manifest V3. The Chrome Web Store no longer accepts manifest V2 extensions (see Manifest V2 support timeline for more details). There will be other manifest versions in the future (V4 and beyond), but these aren't scheduled yet.