Denver, Colorado
Area code 303 phone validation
Calling or texting a list of 303 numbers? Check every number first: valid or dead, mobile, landline or VoIP, and the carrier it is on now.
Start 7-day free trial →What validating 303 numbers tells you
- ✓Valid or dead. Disconnected and unassigned 303 numbers are flagged before your dialer or SMS tool reaches them.
- ✓Mobile, landline or VoIP. Know which numbers can take a text and which are desk phones or app numbers.
- ✓Carrier. The carrier each number is on now, which can differ from the company that was first given the prefix because numbers are ported.
Who holds 303 prefixes
Companies holding the most 303 prefixes (NPA-NXX blocks) in the NANPA utilized-codes report. This is who was assigned the number blocks, not who serves each number today: a number can be ported to any carrier, which is why a live check matters.
| Qwest | 448 prefixes |
| Verizon Wireless | 60 prefixes |
| Level 3 Communications | 58 prefixes |
| T-Mobile Usa | 39 prefixes |
| New Cingular Wireless Pcs | 35 prefixes |
| Spok | 31 prefixes |
104 of 784 303 prefixes are held by companies that commonly supply numbers to VoIP and texting apps.
Places served by 303
Denver, Longmont, Fortlupton, Deckers, Keenesburg, Hudson, Georgetown, Deer Trail.
Upload your 303 list as CSV or Excel. Every number comes back marked valid or dead, mobile, landline or VoIP, with carrier.
Starter: $97/month for 5,000 numbers after the 7-day trial. Cancel anytime.
Questions
Where is area code 303?
303 serves Denver, Colorado, including places such as Longmont, Fortlupton, Deckers. Time zone: Mountain Time (MT).
Which area codes overlap with 303?
720, 983 serve the same area. A list for this area will usually mix these codes, and TrueSearch checks them all the same way.
Does a 303 number mean the person is in Colorado?
Not always. People keep their numbers when they move or switch carriers, and VoIP numbers can be assigned anywhere. The area code tells you where the number was first assigned, not where the person is today.
What does validating a 303 number tell me?
Whether the number is valid or dead, whether it is a mobile, landline or VoIP line, and the carrier it is on now, from live carrier data.
Does TrueSearch check Do Not Call lists?
No. TrueSearch does not check the National Do Not Call Registry, state DNC lists or litigator lists yet. Run those checks separately where they apply.
303 prefix pages
More Colorado area codes
Area code 303 reference: places, prefixes and local time
This guide is general information, not legal advice. TrueSearch for Business checks validity, line type and carrier from licensed telecom data. It does not check the National Do Not Call Registry, state DNC lists or the FCC Reassigned Numbers Database. Not a consumer reporting agency; not for FCRA purposes.