Google lured billions of consumers to its digital services by offering copious free cloud storage. That is beginning to change.

The Alphabet Inc. unit has whittled down some free storage offers in recent months while prodding more users toward a new paid cloud subscription called Google One. That is happening as the amount of data people stash online continues to soar.

When people hit those caps, they realize they have little choice but to start paying or else risk losing access to emails, photos and personal documents. The cost isn't excessive, but at the scale Google operates, this could generate billions of dollars in extra revenue each year for the company.