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

The Alphabet 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's happening as the amount of data people stash online continues to soar.

Google shook up the email business when Gmail launched in 2004 with much more free storage than rivals were providing at the time. It boosted the storage cap every couple of years, but in 2013 it stopped. Credit:John Davidson

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

A big driver of the shift is Gmail. Google shook up the email business when Gmail launched in 2004 with much more free storage than rivals were providing at the time. It boosted the storage cap every couple of years, but in 2013 it stopped. People's inboxes kept filling up. And now that some of Google's other free storage offers are shrinking, consumers are beginning to get nasty surprises.