303 Area Code — Denver, CO
Area code 303 serves Denver and 4 other cities in Colorado. Local time follows America/Denver. It overlays with 720, 983, so 10-digit dialling is required.
- State
- Colorado
- Primary city
- Denver
- Timezone
- America/Denver
- In service since
- 1947
- Type
- Geographic
Cities Served by 303
The 303 area code covers 5 cities and communities in Colorado.
- Denver
- Aurora
- Lakewood
- Boulder
- Westminster
About Area Code 303
Area code 303 is a North American Numbering Plan (NANP) area code that has been in service since 1947. It is administered by NANPA on behalf of the FCC and serves the Colorado region anchored on Denver.
303 now shares its territory with overlay codes (720, 983). 10-digit dialling is required for local calls within this region because the same 7-digit number can be assigned under either code.
Mobile numbers in 303 are portable: a person who moved away from Denver may still carry a 303 mobile number on their device. If you receive an unexpected call from a 303 number, run it through the reverse lookup tool above for the most accurate, free identification.
If you live or do business in Colorado, you may also interact with neighbouring or overlay codes (720, 983). See the related codes section below to explore the rest of Colorado.
Other Colorado Area Codes
Continue exploring the Colorado numbering plan.
303 Area Code FAQ
Where is area code 303?
Area code 303 is located in Colorado, primarily serving Denver and surrounding cities including Aurora, Lakewood, Boulder. The region operates on MT (America/Denver) time.
What state is 303 area code?
303 is a Colorado area code. It was put into service in 1947 and shares its geographic footprint with overlay codes 720, 983.
Is 303 a scam area code?
303 is a legitimate North American area code allocated by NANPA to Colorado. Like any geographic area code, scammers sometimes spoof 303 numbers — judge each call by content (urgent demands, unfamiliar transfers) rather than the area code alone. Run the specific number through our reverse lookup if you're unsure.
What time zone does 303 use?
Area code 303 operates on MT (America/Denver). Numbers in this area code follow standard Colorado time-zone rules including any daylight-saving transitions for that region.
Can I look up a specific 303 phone number?
Yes. Use the reverse lookup widget above to enter a full 303 number. NumLocation returns the line type (mobile, landline, VoIP), carrier, rate-center city, and any public listings tied to the number — free.
What's the difference between 303 and 720?
303 and 720 cover the same Colorado geographic area as overlay codes. Calls between them are local, but you must dial all 10 digits. New phone numbers in this region are assigned from either pool depending on what's available with the carrier at signup.