NANP area code
341
UTC−8, UTC−7 during daylight saving
- State
- California
- Primary city
- San Francisco
- Time zone
- Pacific
- In service
- 2019
- Overlay
- 510
NANP area code
341
UTC−8, UTC−7 during daylight saving
The code reaches 35 communities and 6 counties across California.
The area code itself carries no risk signal. 341 is assigned to San Francisco, California, so a call from it is consistent with a real caller in that area — but the digits alone prove nothing, because they can be forged.
Caller ID is set by whoever places the call, not verified by the network. That is why neighbour spoofing works: an operation anywhere in the world can display a number that matches the area code — and often the first three digits after it — of the person being called, so the call looks local. Every community in the 341 territory is a plausible-looking origin for a forged 341 number, which is why one can be made to look like a neighbour to so many people. The same applies to its overlay code 510, which serves the same ground.
If you did not recognise the call: let it go to voicemail — a legitimate caller with real business will leave one. Do not return the call using the number shown; look the organisation up independently and call the number you found. Never confirm personal details, card numbers, or one-time codes to someone who called you, however plausible the number looked.
Codes.zone publishes no complaint counts, risk scores, or caller identities. We hold no data on individual numbers and will not estimate what we cannot source.
Time there now
—
Pacific · UTC−8, UTC−7 during daylight saving
Reasonable callback window
8:00 AM – 9:00 PM
local time in Pacific
Federal rules bar telemarketing calls to a residence outside 8:00 AM–9:00 PM in the called party's own time zone. It is a sensible bound for a personal callback too — and a caller who rang you well outside it was not observing it.
341 does not have its territory to itself. 510 covers the same ground, serving San Francisco and the rest of the 341 territory. An overlay is what a regulator adds when a region runs out of assignable numbers: rather than splitting the area and forcing half the residents to change their number, a second code is laid over the top and new numbers are issued from it.
The practical consequence: two neighbours on the same street can hold numbers in different area codes, so the code tells you nothing about which part of town a caller is in — and local calls must be dialled as all ten digits, because seven is no longer unambiguous.
| City | ZIP codes | County |
|---|---|---|
| San Francisco | 51 | San Francisco County |
| Oakland | 26 | Alameda County |
| Berkeley | 11 | Alameda County |
| Hayward | 7 | Alameda County |
| Richmond | 7 | Contra Costa County |
| Fremont | 5 | Alameda County |
| Walnut Creek | 4 | Contra Costa County |
| San Leandro | 3 | Alameda County |
| Alameda | 2 | Alameda County |
| Antioch | 2 | Contra Costa County |
| Castro Valley | 2 | Alameda County |
| Corte Madera | 2 | Marin County |
| Danville | 2 | Contra Costa County |
| El Sobrante | 2 | Contra Costa County |
| Emeryville | 2 | Alameda County |
| Fairfield | 2 | Solano County |
| Livermore | 2 | Alameda County |
| Menlo Park | 2 | San Mateo County |
| Pleasanton | 2 | Alameda County |
| San Quentin | 2 | Marin County |
15 further communities not listed. All California area codes →
Scope every community matched to 341. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot), GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated . Coordinates are place reference points, not boundaries.
We do not publish the NXX prefixes inside 341. The assignment of prefixes to rate centres comes from LERG routing data, which is proprietary, and we will not estimate it from postal data — ZIP codes and telephone prefixes do not map onto each other. Awaiting a clean-rights NPA-NXX source.
341 is the newer code here, added in 2019 over 510 (1991). The older code had run out of exchanges to assign, and an overlay avoids the alternative — splitting the region and forcing half its residents to renumber. New lines have been issued from 341 since.