Area code 303 – Colorado
303 is one of the original area codes, in service across Colorado since 1947. All but a handful of its 786 number blocks are allocated (784 of 786), so it is effectively exhausted. Lumen / CenturyLink holds 64.8% of those blocks, which is unusually concentrated for a US area code. It shares its geography with overlay codes 720, 983, so local calls take all ten digits. 927 FTC complaints named a 303 caller ID in the 33 days to 30 October 2026, putting it 53rd of 422 codes with five or more complaints.
- State
- Colorado
- In service since
- 1947
- Time zone
- Mountain
Who holds 303 number blocks
Share of the 784 assigned NXX blocks (99.7% of the 786 possible), across 27 carriers. This is share of number blocks, not of subscribers.
- Lumen64.8%
- Verizon11.6%
- AT&T8%
- T-Mobile5%
- Spok4%
- Onvoy1.8%
- Other CLEC / VoIP1.8%
- American Messaging1.4%
- Comcast0.9%
- Allstream0.4%
- Charter0.3%
- Windstream0.1%
Spam complaints naming 303
FTC Do Not Call complaints where the caller ID was a 303 number, 28 Sep – 30 Oct 2026 (33 days). Caller IDs on spam calls are frequently spoofed, so these are complaints about the code, not calls proven to originate in it.
Rate centers in 303
NANPA allocates number blocks to rate centers and records their names abbreviated to ten characters, so these are NANPA's codes rather than place names – CHAMPAURBN is Champaign-Urbana, NWYRCYZN01 is a New York City zone. We show them unchanged instead of guessing at the full names. Showing the largest 5 of 13.
Timeline
- 1947 303 assigned in the original North American Numbering Plan.
More about 303
Separate pages for the questions that need their own answer: what time it is there, what the complaint data says, who holds the number blocks, and how the code compares with the one it shares its area with.
Frequently asked about 303
What state is area code 303?
Colorado. It covers the same area as 303/720/983.
Can I still get a 303 number?
Only from recycled stock. 784 of the 786 available blocks are already allocated, so new numbers in the area normally come from the overlay codes (303/720/983).
Is a call from 303 a scam?
Not by itself. 303 drew 927 FTC complaints in the 33 days to 30 October 2026, 53rd of 422 ranked codes – mid-pack or lower. Spam callers spoof caller IDs, so the only useful check is the full number.
Which carrier owns 303 numbers?
Lumen / CenturyLink holds the largest share of assigned number blocks at 64.8%. The rest is spread across 3 other carriers. This is share of number blocks, not of subscribers – people keep their numbers when they switch carriers.
Do I need to dial 10 digits in 303?
Yes – ten digits for local calls in 303, because it shares its area with another code.
Sources and verification
- NANPA – NPA Database (npa_report.csv), file date 11/01/2026, retrieved Nov 1, 2026
- NANPA – CO Code Assignment Records, All States (utilized), file updated 11/01/2026, retrieved Nov 1, 2026
- FTC – Do Not Call Reported Calls Data, 25 daily files 28 Sep – 30 Oct 2026, retrieved Nov 1, 2026
NANPA dialing note for this code: “10D”. Reviewed by the data desk. Spotted an error? Request a correction.