Operators of commercial websites or online services that collect personal information would be required to disclose on their sites whether they honor "do not track" signals from users.
Under AB370, they also would have to say whether other parties can collect personal information from consumers' use of that website.
The state attorney general's office says websites frequently install invisible tracking devices on users' computers, including some that reinstall themselves even after users try to delete them.
The bill by Democratic Assemblyman Al Muratsuchi of Torrance would require sites to disclose their policies.
It was approved 36-0 Thursday and returns to the Assembly for a final vote on amendments.