How can you tell if a ring online is real sterling silver?

'Sterling' silver is real silver. Any item that is described as 'Sterling' silver will always be real silver as 'Sterling' is actually the name gives to the 925 purity of silver. Sterling is 92.5% purity. This is the standard of real silver as we know it.

It will also be hallmarked with the number of fineness at 925, as classified internationally as Sterling Silver.