A state privacy law that took effect on Wednesday gives residents the right to see, correct and delete personal data held by companies, and to opt out of having it sold.

Companies that collect data on more than 100,000 residents must comply. The state attorney general’s office said it would focus early enforcement on data brokers.

“For most people, the first step is just finding out who has your data,” said privacy advocate Lucia Ferreira. “Now you have a legal right to ask.”