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.
Packaged app developers must currently specify
'manifest_version': 2:
{
...,
"manifest_version": 2,
...
}
Manifest version 1 only applied to extensions and hosted apps, not packaged apps. It was deprecated in Chrome 18.