California · Pacific Time
510 Area Code
Area code 510 is in California, serving western Alameda and Contra Costa counties on the East Bay, including Oakland and Fremont. It is in the Pacific Time zone. It shares its territory with overlay code 341, so 10-digit dialing is required.
Last updated October 1, 2026 · Source: NANPA
Where is the 510 area code?
510 is a California area code covering western Alameda and Contra Costa counties on the East Bay, including Oakland and Fremont. In the wider directory it sits in the West region.
Cities in the 510 area code
- Oakland
- Fremont
- Hayward
- Berkeley
- Richmond
- San Leandro
- Alameda
- Union City
- Newark
- San Pablo
- El Cerrito
- Emeryville
- Albany
- Hercules
Counties served by 510
Alameda County and Contra Costa County.
510 overlay codes and dialing
The 510 territory is covered by an overlay of 2 area codes: 341, 510. All of them serve the same geographic area, and the original code is 510. Because more than one code covers the same ground, 10-digit dialing is mandatory — you must dial the area code for every local call. New phone lines may be assigned any of these codes.
History of the 510 area code
510 went into service on September 2, 1991, created when it was split from 415. It serves Oakland and the surrounding part of California, and today shares its territory with overlay code 341. For how codes are created, split, and overlaid, see how area codes work.
Is 510 a scam or spam risk?
510 is a legitimate geographic area code, not a premium or toll line, so a call from it costs you nothing extra. That said, scammers frequently spoof real local area codes to look familiar on caller ID. A genuine 510 number on your screen is no guarantee the caller is in Oakland, CA or trustworthy. See spam & scam-risk area codes for how spoofing works and how to respond.
Other California area codes
Explore more
See every code in California, compare codes across the West region, or view all Pacific Time codes. You can also browse the 5XX block or the complete numeric list of US area codes.
New to how this all works? Start with how area codes work, then read up on overlays, 10-digit dialing, and spam & scam-risk codes. To check another number, use the area code lookup tool.
Quick answers
510 area code FAQ
Where is the 510 area code?
The 510 area code is in California, covering western Alameda and Contra Costa counties on the East Bay, including Oakland and Fremont, in the West region.
What cities are in the 510 area code?
Cities in the 510 area code include Oakland, Fremont, Hayward, Berkeley, Richmond, San Leandro, Alameda, Union City, Newark and San Pablo.
What time zone is 510 in?
510 is in the Pacific Time zone.
What is the overlay for the 510 area code?
510 shares its territory with 341. Both codes (341, 510) serve the same area, so 10-digit dialing is required for every call.
When did the 510 area code start?
510 went into service on September 2, 1991.
Do I have to dial 10 digits for 510?
Yes. Because 510 is an overlay area, you must dial the full 10-digit number (area code + 7 digits) for every call.
Is 510 a toll-free or premium code?
No. 510 is a standard geographic area code, so calling it costs the same as any local or long-distance call on your plan. Toll-free calls use 800, 888, 877, 866, 855, 844 or 833.