Manifest Version

Applications are simply bundles of resources, wrapped up with a manifest.json file that describes the package's contents. The format of this file is generally stable, but occasionally breaking changes must be made to address important issues. Developers should specify which version of the manifest specification their package targets by setting a manifest_version key in their manifests.

Current Version

Chrome App developers must currently specify 'manifest_version': 2:

  "manifest_version": 2,

Manifest version 1 only applied to extensions and hosted apps, not Chrome Apps. It was deprecated in Chrome 18.