A coalition of Internet watchdogs replaced the bat signal with a cat signal, projected onto the Bay Bridge from Mozilla's headquarters on Harrison Street.
The cat signal was part of the launch of the Internet Defense League to defend the Web against government over-regulation. Mozilla wants its cat signal to be the new symbol of Internet freedom.
Cat lights were also shined on tech buildings aligned with the league in New York, Washington DC and London.
That light in San Francisco was so bright the cops were called to check it out.