CALIFORNIA: Facebook has upgraded its private-photo sharing mobile app 'Moments' which now allows users to share a URL link of their private albums with anyone online ─ even those who are not connected with the uploader on the social media site, Tech Crunch reports.

The public link will let other viewers join the album and even add their own photos. This feature could come in handy when people want to collaborate on larger events such as weddings or parties.

Previously 'Moments' only allowed users to share photos and albums with their friends on Facebook.

The app had previously replaced 'Mobile photo Sync' that let users upload their mobile photos to the Facebook server as a backup. Moments gave users the same backup facility along with other options like sharing and photo editing.

The latest upgrade adds in support for hi-res photograph storage. Users can select their favorite photographs which will be automatically saved in original resolution while the standard back up option optimizes photos for mobile usage.

Storage for both quality of pictures continues to be free.

This upgrade from Facebook seems to be a direct response to the recent additions made to Google 'Photos' - a similar photo storage app.

'Photos' provides unlimited storage for mobile photos at a low-res quality along with 15GB for backing up full resolution photos. Users can buy more storage space if required. The app also has a commenting feature and lets users add photos to shared albums.

The main difference between the two apps right now is the flexibility offered in storage of hi-res photographs.

With 'moments' users can choose which photographs are important enough to be backed up in full size and there is no additional cost to how many hi-res pictures they want to save.