Area Code Guides
Learn what an area code means, what it can (and can’t) tell you about a phone number, and what changes when new codes are added—like overlays, splits, and 10-digit dialing.
How Area Codes Work
Learn the basics of NPAs, the NANP number structure, and why dialing rules change.
Overlay vs Split
Understand the difference between the two most common NPA relief methods and what they mean for 10-digit dialing.
Unknown Number Safety
What to do when you receive a call from an unfamiliar number — how to identify scam calls, block them, and report to the FTC and FCC.
Area Code History
How the NANP grew from 77 US area codes in 1947 to 374 in service today, and why splits gave way to overlays.
10-Digit Dialing
Why overlay area codes require all 10 digits for local calls, and which US regions have already made the switch.
Why Area Codes Exhaust Faster in Some States
Data-driven analysis of why 158 US area codes exceed 90% utilization, and why exhaustion rates vary dramatically by state.
What Area Codes Can and Can't Tell You
Area codes reveal a geographic region, not a precise location. Common misconceptions and what the data actually shows.
Area Code vs ZIP Code vs Exchange
The three levels of a US phone number explained: area code (NPA), exchange (NXX), and subscriber number — plus how they differ from ZIP codes.
How New Area Codes Are Assigned
The process behind creating new US area codes: who assigns them, when relief is needed, and how the split vs overlay decision is made.
About these guides
These articles focus on common questions people search for—what an area code means, why new codes are added, and what changes when an overlay or split is introduced. For the dataset behind this site, see Data Sources.
If you’re looking for a specific code, browse the area codes directory.