North American Numbers Source-cited · ownership disclosed
Area code
631
In service
United States · since 1999

Suffolk County

Serves Suffolk County on eastern Long Island, split from 516 in 1999.

The essentials Numbering data · NumberResearch · as of 2026-09-18
Place
Suffolk County
Type
geographic
Status
in service
In service since
1999
Projected exhaust
2079 Q3

Status, dates and counts are read from NumberResearch (NANPA / CNAC / FCC records). Assignment records show initial assignees, not the carrier serving a number today.

A · Where it is

Where 631 is

Suffolk County, Long Island, New York.

Communities served wholly or partly by 631:

BabylonHuntingtonIslipSmithtownBrookhavenRiverheadSouthamptonEast Hampton

Representative; includes the Hamptons and the East End.

B · Relationships

How it relates to other codes

The codes 631 was split from, spawned, or shares its area with. A split divides the map and changes some numbers; an overlay shares the same ground and changes none — what's the difference?

Split from · 1999 516 Nassau County Split from 516 on Nov 1, 1999.
Overlay · 2016 934 Suffolk County (overlay) 934 overlays 631.
What's changing. Overlaid by 934 across Suffolk County; ten-digit dialing required.
C · History

How 631 got here

1999-11-01
Created exclusively for Suffolk County; permissive dialing continued to April 1, 2000.
Source: Wikipedia 631/934
2016
934 overlay assigned as 631 neared central-office-code depletion.
Source: Wikipedia 631/934
D · Capacity

How full it is

Prefixes assigned
799
Prefixes available
1
Thousands-blocks assigned
4,219

Prefix-assignment counts describe allocation to carriers, not how many individual numbers are in use. Full technical records: NumberResearch ↗.

Compare 631 with another code →
Sources
Wikipedia (secondary) ↗
Area codes 631 and 934
NumberResearch.org ↗
Live status, dates, assignment counts and exhaust forecast — data as of 2026-09-18 (CC BY 4.0).

Place, relationships and history above are compiled by North American Numbers from the sources listed and last checked 2026-09-18. A check date is not an expert review — see how this is made. Flag an error.