Enabling Anonymous SharePoint 2013 REST API Calls
Introduction
Even after enabling Anonymous Access, developers face issues while making SharePoint 2013 REST API calls.
Diagnostic Steps
By default, REST API calls fail even if the SharePoint portal is configured for Anonymous Access.
This is due to the fact that the ViewFormPagesLockDown Feature (Site Collection) in SharePoint 2013 is activated and visible by default. This was not the case with previous versions of SharePoint.
Resolutions
The following settings need to be set to overcome this issue:
Please navigate to Site Collection settings and deactivate the feature "Limited Access user permission lockdown mode".
Assumption: Already Anonymous Access has been configured at Central Admin level and other required libraries as and where required.
NOTE: Special thanks to my colleague Geethu Soman who help me conclude the same.