The 631 area code serves Suffolk County — the eastern two-thirds of Long Island, New York. Created in 1999 when it split from 516, it covers everything from the busy suburbs of western Suffolk to the beaches of the Hamptons and the North Fork. If a 631 number has appeared on your caller ID, this guide explains where it comes from, how to dial it, and how to protect yourself from spoofed calls.
Quick Summary: Area Code 631 at a Glance
| Detail | Information |
|---|---|
| Area Code | 631 |
| State | New York (NY) |
| Major Cities | Brookhaven, Islip, Huntington, Riverhead (Suffolk County) |
| Time Zone | Eastern Time (ET) |
| Country Code | +1 (USA) |
| Overlay Codes | 934 |
Geographic Coverage & Major Cities
Area code 631 covers Suffolk County, the eastern portion of Long Island stretching from the Nassau County line all the way to Montauk Point. It is a large county mixing dense suburbs, farmland, and famous shoreline resort communities.
Towns and communities served by the 631 area code include:
- Brookhaven and Islip — Suffolk’s largest towns, spanning much of the central island
- Huntington and Babylon — western Suffolk’s busy commuter suburbs
- Riverhead and the North Fork — the gateway to Long Island wine country
- The Hamptons and Montauk — the South Fork’s renowned beach resort towns
As the phone code of eastern Long Island, a 631 number carries a distinctly Suffolk County identity valued by residents and local businesses.
A Brief History of Area Code 631
Area code 631 was created in 1999, split from 516 as Long Island’s population outgrew a single code. The split assigned 516 to Nassau County (inner Long Island) and 631 to Suffolk County (outer Long Island). To add further capacity, the 934 overlay was introduced across Suffolk in 2016, bringing mandatory 10-digit dialing to the region.
Time Zone & Best Time to Call
Numbers in the 631 area code operate on Eastern Time (ET). The region observes Daylight Saving Time, switching from EST (UTC−5) to EDT (UTC−4) between March and November.
How to Dial Phone Numbers in Area Code 631
Because of the 934 overlay, Suffolk County requires 10-digit dialing for every call.
Calling within the United States or Canada
- 10-digit dialing: Always include the area code — 631-XXX-XXXX.
- 11-digit dialing: You can also dial 1-631-XXX-XXXX; the leading 1 is the NANP country code.
Calling from outside the United States
- Format: [exit code] + 1 + 631 + XXX + XXXX
- From the UK, Europe, or most of Asia/Africa: 00 1 631 XXX XXXX
- From any mobile phone worldwide: +1 631 XXX XXXX
Is Area Code 631 a Scam? Safety & Protection Tips
Area code 631 is a legitimate New York area code, so a 631 call is not fraudulent by default. However, scammers frequently spoof the code so their calls appear to come from a trusted local Long Island number. Neighbor spoofing, which imitates your own number’s first six digits, is especially common in high-population suburbs like Suffolk County.
Common scam tactics linked to this region
| Scam type | What to watch for |
|---|---|
| Bank & card impersonation | Alerts about “suspicious activity” seeking your account details |
| Government impersonation | Callers posing as the IRS or SSA threatening legal action |
| Home-services scams | Fake calls about “required” repairs, warranties, or inspections |
| Debt-collection fraud | Pressure to pay a debt you do not recognize |
How to report, block, and look up 631 callers
- Never share personal or banking details with an unexpected caller.
- Block the number using your phone’s built-in feature or a reputable call-screening app.
- Look up the number with a trusted reverse phone lookup before calling back.
- Report it to the FTC at reportfraud.ftc.gov and register at DoNotCall.gov.
Nearby & Related Area Codes in New York
Area code 631 borders several other downstate New York codes:
- 934 — the overlay covering the same Suffolk County territory
- 516 & 363 — Nassau County, the rest of Long Island to the west (see our 516 area code guide)
- 718, 347 & 929 — Queens and the other NYC outer boroughs (see the 718 area code)
- 212, 646 & 917 — New York City proper (read about the 212 area code)
Explore more codes across the state on our New York area codes hub, or browse every prefix in our US area codes directory.
↑ See the complete list of All US Area Codes by State – every area code across all 50 states in one directory.
Explore Neighboring States
Researching area codes just across the state line? Start with these codes in the states that border New York:
- New Jersey – area code 201
- Pennsylvania – area code 215
- Connecticut – area code 203
- Massachusetts – area code 617
- Vermont – area code 802
Frequently Asked Questions About Area Code 631
Where is the 631 area code located?
Area code 631 covers Suffolk County on eastern Long Island, New York, including Brookhaven, Islip, Huntington, Riverhead, and the Hamptons. It operates on Eastern Time and shares its territory with the 934 overlay.
Is 631 a landline or cell phone area code?
Both. Area code 631 serves landlines, mobile phones, and VoIP numbers throughout Suffolk County.
What is the difference between 631 and 516?
631 covers Suffolk County (eastern Long Island), while 516 covers Nassau County (inner Long Island). The two split in 1999 as Long Island’s population grew.
Should I answer a call from an unknown 631 number?
If you are not expecting the call, let it go to voicemail. Legitimate callers leave a message, while spoofed or robocall numbers usually will not. Verify any unfamiliar number with a reverse lookup before calling back.
Related 631 Guides
- Worried about spam or robocalls? Browse our Scam Alerts directory.