What is what area code is 680?

Area code 680 is an overlay area code that covers the same geographic area as area code 510 in California. It was implemented in September 2018 to provide numbering relief for the 510 area code as the available phone numbers were running out. The 680 area code serves cities such as Berkeley, Oakland, Fremont, and Hayward. Calls within the same area code require 10-digit dialing, even for local calls.