Area codes · +1
Area code 203
Area code 203 is centred on New Haven, Connecticut. We hold 5,514 allocated blocks for it across 33 rate centres, split 47% mobile, 48% landline and 6% VoIP.
The other area codes laid over 203
Area code 203 does not have New Haven to itself. 1 other code — 475 — serves the same rate centres, laid over the same ground rather than dividing it. That is an overlay: a new code added when the old one ran out of numbers, covering the same streets. Two neighbours can hold different area codes, so the code says roughly when a number was issued rather than where it sits.
4753,039 blocks, 32 rate centres, mostly mobile
Each holds its own blocks and its own carrier mix, so a 203 number and a 475 number from the same street can report different line types. Filtering New Haven by area code needs all 2 of them.
203 is not confined to New Haven itself: its blocks sit across 33 rate centres, named in the table below.
Connecticut is split across 4 area codes — 860, 203, 475, 959. By allocated blocks 203 is the second largest of them, holding 34% of the Connecticut total.
Where 203 numbers are concentrated
Rate-centre names are reproduced as NANPA records them. The agency truncates them to ten characters, so longer names appear shortened elsewhere on this site.
| Rate centre | Blocks | Share of 203 |
|---|---|---|
| New Haven | 875 | 16% |
| Stamford | 737 | 13% |
| Bridgeport | 624 | 11% |
| Norwalk | 400 | 7% |
| Waterbury | 352 | 6% |
| Danbury | 351 | 6% |
| Greenwich | 207 | 4% |
| Meriden | 164 | 3% |
| Ansonidrby | 137 | 2% |
| Darien | 135 | 2% |
| Fairfield | 114 | 2% |
| Westport | 106 | 2% |
| Wallingfd | 104 | 2% |
| Huntington | 94 | 2% |
| Trumbull | 92 | 2% |
| Oldgrnwich | 88 | 2% |
| Milford | 84 | 2% |
| Cheshire | 80 | 1% |
| Woodbury | 78 | 1% |
| Byram | 77 | 1% |
| New Canaan | 77 | 1% |
| Branford | 70 | 1% |
| Guilford | 68 | 1% |
| Wilton | 68 | 1% |
9 further rate centres in 203 hold fewer blocks than these.
Carriers holding the most 203 blocks
Southern New England Telco Dba Frontier Comm Of Ct1,288 blocks
Verizon Wireless522 blocks
T-Mobile USA, Inc.396 blocks
AT&T Wireless372 blocks
Bandwidth319 blocks
Omnipoint Communications, Inc.303 blocks
The largest holder, Southern New England Telco Dba Frontier Comm Of Ct, has 23% of the code.
These are original allocations. A number keeps its digits and its block when its subscriber moves network, so a ported 203 number still reports the carrier it started with. Closing that gap needs a live query against the routing database. How line type is derived.
Check a single 203 number, or run a whole list through the free cleaner — neither uploads anything.
Common questions
Where is area code 203?
Area code 203 covers New Haven, Connecticut. It is not the only code there: 475 is an overlay on the same rate centres, so a New Haven, Connecticut number can start with any of them.
Is a 203 number a mobile or a landline?
It can be either, and the digits do not say which. North American mobile and landline numbers share the same ranges, so the answer comes from the carrier holding the block. In 203 the split runs 47% mobile, 48% landline and 6% VoIP, so landline is the most likely single answer.
Which carriers hold 203 numbers?
The largest holders are Southern New England Telco Dba Frontier Comm Of Ct, Verizon Wireless, T-Mobile USA, Inc.. That is the carrier the block was allocated to, which is not necessarily the network a given number sits on today.
How many 203 numbers are there?
The code holds 5,514 allocated blocks in our copy of the numbering plan. A block is 1,000 or 10,000 consecutive numbers depending on how deeply it has been pooled, so 203 covers on the order of 5,514,000 possible numbers — most of which have never been issued to anyone.