How to Look Up a US Phone Prefix (NPA-NXX): Rate Center, State and Original Carrier
An NPA-NXX lookup reads the first six digits of a US phone number and returns what NANPA's records hold for them: the rate center, state, LATA and the carrier the prefix was assigned to. Type a prefix or paste whole numbers into the NPA-NXX lookup. For a full number it also reads the thousands digit, because a pooled prefix can be split between carriers in blocks of 1,000.
Look it up with the tool
- Open the NPA-NXX lookup.
- Type a prefix such as
312-200, or paste phone numbers one per line. A CSV works too; the phone column is found automatically. - Press Look up NPA-NXX. One entry shows the full record; a list shows a table.
- Download the list with state, rate center, LATA, original carrier and OCN added.
Look it up in NANPA's file
NANPA publishes its central office code assignment records as zipped, tab-separated text. We ran this on 8 November 2026; the file said it was updated the same day and had 205,308 lines:
curl -sLO https://reports.nanpa.com/public/CoCodeAssignment_Utilized_AllStates_Public.zip
unzip -q CoCodeAssignment_Utilized_AllStates_Public.zip
awk -F'\t' '$2=="312-200" {for(i=1;i<=NF;i++) gsub(/^ +| +$/,"",$i); print $1" | "$2" | "$4" | "$5" | pooled "$10}' \
CoCodeAssignment_Utilized_AllStates_Public.txt
# IL | 312-200 | "METROPCS, INC." | CHICGOZN01 | pooled Y
The columns are state, NPA-NXX, carrier, rate center and whether the code is pooled. Pooled Y means the prefix is handed out in 1,000-number blocks, which can belong to different carriers. Those are in NANPA's separate thousands-block reports, which the tool also reads.
What the record does and doesn't tell you
- Where the number was issued. The rate center and state are reliable for the prefix.
- The original carrier. Numbers can move between carriers and keep their digits, so today's carrier may differ. See phone carrier lookup.
- Not the line type. US mobiles and landlines share prefixes. See mobile vs landline lookup.
- Not whether the line is in service or who uses it.
Next step: the email column next to the phones
A lead list with phone prefixes almost always has emails too. Upload it at /verify to check every mailbox without sending. The first 100 checks are free with a Google sign-in, no card.
Pro, $39 a month: Unlimited email verification.* Never metered, never cut off. Live carrier lookups are a separate phone add-on with a monthly allowance. See pricing.
*Fair use: the first 100,000 checks a month at full speed, then slower, never cut off.
More: US phone number format, extract phone numbers from text.
Common questions
What is an NPA-NXX?
The first six digits of a North American number: the three-digit area code (NPA) and the three-digit central office code (NXX). In 312-200-xxxx, the NPA-NXX is 312-200.
How do I find which carrier a phone prefix belongs to?
Enter the prefix or a full number in the NPA-NXX lookup. It shows the carrier NANPA assigned the prefix, or its 1,000-number block, to.
Is the carrier from an NPA-NXX lookup the current carrier?
Not necessarily. A number keeps its digits when it's ported to another carrier, so the prefix shows the original assignee. A live carrier lookup shows the current one.
Does it work for Canadian numbers?
No. Canadian prefixes are administered separately and aren't in NANPA's US files.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.