🇺🇸 303 area code
Area code 303 covers Denver, Aurora, Boulder and Littleton and the surrounding area in Colorado. It shares that territory with 720 and 983, so the same neighbourhood can have numbers in any of them. Enter a 303 number below for a free check before you call back.
- Location: Denver, Colorado
- Time zone: Mountain (UTC−7)
- In service since 1947
Nummer abfragen
Gültigkeit, Anbieter, Leitungstyp und Region im ersten Durchgang.
Area code 303 at a glance
- Area code
- 303
- Location
- Colorado, United States
- Main cities
- Denver, Aurora, Boulder, Littleton, Golden, Longmont
- Time zone
- Mountain (UTC−7)
- Local time now
- —
- In service since
- 1947
- Overlay codes
- 720, 983
- Codes split from it
- 719, 720, 970, 983
- Local calls
- Dial 10 digits
- Number format
- (303) 555-0123
- From abroad
- +1 303 555 0123
Cities in area code 303
- Denver
- Aurora
- Boulder
- Littleton
- Golden
- Longmont
- Broomfield
- Lakewood
- Englewood
- Brighton
Is a 303 call a scam?
An area code tells you where a number was first assigned, not where the caller is. Mobile numbers keep their area code when people move, and internet (VoIP) numbers can be picked in any area code — so a 303 number can be calling from anywhere.
Robocallers exploit that with "neighbor spoofing": showing a 303 number to people in Colorado because a local-looking call is more likely to be answered. If a 303 call claims to be your bank, the IRS or a delivery company, hang up and call the official number yourself.
About area code 303
303 is one of the original North American area codes, created in 1947 when AT&T and the Bell System first divided the continent into numbering plan areas.
It is part of the 303/720/983 overlay: the codes cover the same area, and a new line there can be given a number in any of them. Two neighbours — or two phones in one household — can have different area codes. That is also why local calls need the full ten digits.
As the region grew, 719, 720, 970 and 983 were carved out of or added to 303.
Area codes
More area codes in Colorado
All Colorado area codes · Every North American area code · International country codes
FAQ
Area code 303 questions
Sources: NANPA NPA database (11/04/2026) and Google libphonenumber. Area codes show where a number was assigned, not where its owner is today.
Where is area code 303?
Area code 303 is in Colorado, United States. It covers Denver, Aurora, Boulder, Littleton, Golden and Longmont.
What time zone is area code 303?
303 is in the Mountain (UTC−7) time zone, and observes daylight saving time.
What area codes overlay 303?
720 and 983 serve the same area as 303. Numbers in all of them are local to one another.
When did area code 303 start?
303 entered service in 1947.
How do I find out who called me from 303?
Enter the full number in the lookup at the top of this page. The free check confirms whether the number is valid and shows its carrier, line type and region; a full report adds owner and public-web records where they are available.
Why am I getting calls from area code 303?
If you live in or near Colorado, they may be genuinely local — or robocalls spoofing a local-looking number. Unknown 303 callers who will not leave a message are best looked up before you call back.
Got a call from 303?
Run the free check first — validity, carrier, line type and region — and unlock the full report only if you need it.