New York · Eastern Time
631 Area Code
Area code 631 is in New York, serving Suffolk County on eastern Long Island, including the Hamptons. It is in the Eastern Time zone. It shares its territory with overlay code 934, so 10-digit dialing is required.
Last updated October 1, 2026 · Source: NANPA
Where is the 631 area code?
631 is a New York area code covering Suffolk County on eastern Long Island, including the Hamptons. In the wider directory it sits in the Northeast region.
Cities in the 631 area code
- Brentwood
- Huntington
- Islip
- Central Islip
- Smithtown
- Commack
- Bay Shore
- Lindenhurst
- Patchogue
- Babylon
- Stony Brook
- Port Jefferson
- Riverhead
- Southampton
- East Hampton
Counties served by 631
Suffolk County.
631 overlay codes and dialing
The 631 territory is covered by an overlay of 2 area codes: 631, 934. All of them serve the same geographic area, and the original code is 631. 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 631 area code
631 went into service on November 1, 1999, created when it was split from 516. It serves Brentwood and the surrounding part of New York, and today shares its territory with overlay code 934. For how codes are created, split, and overlaid, see how area codes work.
Is 631 a scam or spam risk?
631 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 631 number on your screen is no guarantee the caller is in Brentwood, NY or trustworthy. See spam & scam-risk area codes for how spoofing works and how to respond.
Other New York area codes
Explore more
See every code in New York, compare codes across the Northeast region, or view all Eastern Time codes. You can also browse the 6XX 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
631 area code FAQ
Where is the 631 area code?
The 631 area code is in New York, covering Suffolk County on eastern Long Island, including the Hamptons, in the Northeast region.
What cities are in the 631 area code?
Cities in the 631 area code include Brentwood, Huntington, Islip, Central Islip, Smithtown, Commack, Bay Shore, Lindenhurst, Patchogue and Babylon.
What time zone is 631 in?
631 is in the Eastern Time zone.
What is the overlay for the 631 area code?
631 shares its territory with 934. Both codes (631, 934) serve the same area, so 10-digit dialing is required for every call.
When did the 631 area code start?
631 went into service on November 1, 1999.
Do I have to dial 10 digits for 631?
Yes. Because 631 is an overlay area, you must dial the full 10-digit number (area code + 7 digits) for every call.
Is 631 a toll-free or premium code?
No. 631 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.