The 831 area code is located in the state of California, and according to Intelius data, covers roughly 384,441 phone numbers and 528,792 listings across 411 prefixes.
This is a General Purpose Code, in service since July 11, 1998.
Area code 831 was split from area code 408.
Local and long-distance calls within area code 831 both require 7 digits dialing.
Have you received a call from a number with a 831 area code? Figure out who is calling you by performing a reverse phone lookup search. Intelius can provide you with a phone report that includes (when available) original line type and carrier, the number owner’s name, last known address and past addresses, age, possible relatives, and more.
| County Population (2025) | 433,729 |
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| County Population (2025) | 258,852 |
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