The first-of-its-kind "eraser button" law, signed Monday by Governor Jerry Brown, will force social media titans such as Facebook, Twitter and Google let minors scrub their personal online history in the hopes that it might help them avoid personal and work-related problems.
The law will take effect on January 1, 2015.
"Kids so often self-reveal before they self-reflect," James Steyer, founder of Common Sense Media, a nonprofit group in San Francisco that pushed for the law, told the San Francisco Chronicle.
"Mistakes can stay with teens for life, and their digital footprint can follow them wherever they go."
The issue grows increasingly important as the first generation to grow up entirely in the Internet era finds the contents of its online life become more voluminous every day -- as well as being largely searchable.
Social media sites will be required to inform their users about the new rights. Twitter and Facebook already make deleting pictures and comments an option.
"This is a groundbreaking protection for our kids who often act impetuously with postings of ill-advised pictures or messages before they think through the consequences. They deserve the right to remove this material that could haunt them for years to come," said California state senator Darrell Steinberg.
But not everyone is delighted.
For the Family Online Safety Institute (FOSI), the law appears worrisome itself because it will force disclosure of considerable information about minors.
"Instead of protecting their information, (you) actually end up collecting more of their information, because aside the need to know what age the child is, they'll need to know whether they're in California or not," FOSI chief Stephen Balkam told AFP.
He said it also made it more likely that more children would lie about their age online.
Last year, California also passed a law to ban businesses and universities from asking their employees or students for their Facebook account passwords.