The 203 area code covers New Haven, Stamford and 27 more places in Connecticut.
Area code 203 is in Connecticut, on Eastern Time. In the 203 area, phone numbers are given out most in Western Connecticut County, then South Central Regional and Connecticut Metropolitan County. It has been in service since 1947. 475 covers the same area, so two neighbours can have different area codes.
- Where
- 4 counties in Connecticut, mostly Western Connecticut County, South Central Regional and Connecticut Metropolitan County
- Time zone
- Eastern Time
- In service since
- 1947, one of the original area codes
- Shares its area with
- 475 (since 2009)
- Prefixes in use
- 778
- How to dial
- Local calls need all 10 digits: 203-555-0142.
Find out who called you from a 203 number.
Enter the full 10-digit number to see who it is listed to and the city and state on the listing. It is the same free check as our who called me lookup. To see only the caller ID name on the number, use our free CNAM lookup. To see whether it is a mobile, a landline or a VoIP line, use our free VoIP checker. To see which carrier a (203) number is on today, use our free carrier lookup.
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New Haven holds 19% of the phone prefixes in area code 203.
A prefix is the three digits after the area code, and NANPA assigns each one to a town. Counting the 778 prefixes in use shows where 203 numbers are actually given out.
- New Haven145 prefixes, 19%
- Stamford97 prefixes, 12%
- Bridgeport94 prefixes, 12%
- Norwalk60 prefixes, 8%
- Danbury54 prefixes, 7%
- Waterbury52 prefixes, 7%
- Greenwich27 prefixes, 3%
- Meriden24 prefixes, 3%
Also served: Westport, Darien, Fairfield and Wallingford and 17 smaller places.
Frontier holds the most phone number prefixes in area code 203: 332 of 778.
NANPA, which runs the North American numbering plan, assigns each prefix (the three digits after the area code) to one carrier. Here is how the 778 prefixes in use in 203 divide between carriers; holders this page does not name are grouped as other carriers.
| Carrier | Prefixes | Share |
|---|---|---|
| FrontierLandline company | 332 | 43% |
| AT&T MobilityMobile network | 52 | 7% |
| T-MobileMobile network | 47 | 6% |
| Level 3 (Lumen)Lumen's business and wholesale network | 41 | 5% |
| PAETEC (Windstream)Windstream's business phone network | 40 | 5% |
| Teleport (AT&T)AT&T's business phone network | 33 | 4% |
| 14 other carriers | 233 | 30% |
61% of these prefixes are pooled, which means the blocks of 1,000 numbers inside them can belong to other carriers. Any number can also have been moved to another carrier since, so this shows who holds the prefixes, not who serves a given number.
Want the carrier of one exact number? Our free carrier lookup checks it, because numbers move between carriers.
Source: NANPA central office code assignments, October 1, 2026.
203 has been split once and overlaid once since 1947.
1947
203 is one of the original North American area codes.
1995
On August 28, 1995, 860 splits off and takes part of the 203 area.
2009
On December 12, 2009, 475 is added on top of 203, so new numbers here can get either code.
A 203 number on your screen can still be a scam, because caller ID is easy to fake.
- Let an unknown call go to voicemail. A real caller leaves a message; a robocaller usually does not.
- Look the number up with the box above before you call back, because calling back tells a robocaller your line is live.
- Hang up on anyone who wants gift cards, crypto or a wire transfer, or asks you to read out a code that was just texted to you.
- Report unwanted robocalls at reportfraud.ftc.gov, or paste a suspicious message into our free scam checker.
The area codes closest to 203 are 914, 631 and 860.
This list measures the distance between the centres of each area, across state lines, and shows codes that share one area together.
These are the questions people ask most about area code 203.
Where is area code 203?
203 covers New Haven, Stamford, Bridgeport and Norwalk and 25 more places in Connecticut. In the 203 area, phone numbers are given out most in Western Connecticut County, then South Central Regional and Connecticut Metropolitan County.
What state is area code 203 in?
Connecticut. 203 is a Connecticut area code on Eastern Time.
What cities use area code 203?
The places holding the most 203 prefixes are New Haven, Stamford, Bridgeport, Norwalk, Danbury, Waterbury, Greenwich and Meriden, out of 29 places in all. The count comes from NANPA's prefix assignments as of October 1, 2026.
Which phone company owns area code 203?
No single phone company owns 203. NANPA's records show Frontier holds the most 203 prefixes, 332 of 778, followed by AT&T Mobility and T-Mobile. Numbers move between carriers, so check one exact number with a carrier lookup.
What time zone is area code 203 in?
203 is on Eastern Time.
When did area code 203 start?
203 is one of the original North American area codes, in service since 1947.
Is 203 the same area as 475?
Yes. 475 (since 2009) covers the same ground as 203. Nobody's number changed when it was added; new lines simply get whichever code has numbers left, so two neighbours can have different codes.
How do I dial a 203 number?
Local calls need all 10 digits: 203-555-0142.
Is 203 a toll-free number?
No. 203 is a regular area code for New Haven and Stamford in Connecticut, not a toll-free one. The toll-free codes in North America are 800, 833, 844, 855, 866, 877 and 888.
What area codes are near 203?
The closest are 914 (Westchester County, New York), 631/934 (Brentwood, New York), 860/959 (Hartford, Connecticut) and 516/363 (Nassau County, New York), measured between the centres of each area.
Who called me from a 203 number?
Enter the full 10-digit number in the lookup above. It returns the listed owner where there is a public record, where the number is registered, and whether it is a mobile, a landline or a VoIP line.
Is area code 203 a scam?
203 is a real Connecticut area code, so the code itself is not a warning sign. Scam callers fake local-looking numbers on purpose, so judge the call by what the caller asks for, and look the number up before calling back.
Put this lookup on your site: our free area code widget takes two lines of code and shows any US area code's state, time zone and local time.
Source: NANPA, the North American Numbering Plan Administrator: its area code database and prefix assignments, as of October 1, 2026.