https://www.siliconvalley.com/2024/10/01/the-deadline-to-register-to-vote-in-california-and-other-important-dates-for-the-upcoming-election/

County elections offices will soon be sending California households a vote-by-mail ballot for the Nov. 5 election, but you must first be an active registered voter. If you haven’t registered yet, there is still time.  You also have the option to vote by mail or in person. Here are some key dates and what you need to know:

Monday, Oct. 21 is the last day for voter registration online and the last day the mail-in registration can be postmarked.