Not only local ROOT files can be read, but also remote ones. The right TFile specialisation is chosen at runtime automatically by ROOT. The reccomended way of accessing remote files is to use the TFile::Open static function:
auto myFile = TFile::Open("http://root.cern.ch/files/usa.root")
In this case, ROOT automatically recognised from the string "http://" that the class to be used was TWebFile and chose the right plugin. This technique can be applied to a variety of protocols, such as for files on:
Here follows a step-by-step recipe for authentication configuration between ROOT and Amazon S3:
Here follows a step-by-step recipe for authentication configuration between ROOT and Google Storage: