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.