Area code 331 vs 630
331 and 630 are overlay codes: they cover the same ground in Illinois, and a number in one is a local call to the other. 630 is the original, in service since 1996. 331 was added in 2007 because the first was filling up – that is what an overlay is for. Today 331 has 224 of 786 blocks assigned (28.5%) and 630 has 782 of 786 (99.5%), so a new number in the area now almost always comes from 331. In the 33 days to 30 October 2026, 630 drew 844 FTC complaints against 591 for 331 – 84th and 175th of 422 ranked codes. Older codes are spoofed more because they look more established. Neither code is better or safer than the other. They are the same geography, the same carriers and the same dialing rules; the difference is only how long each has existed and how full it is.
Side by side
| 331 | 630 | |
|---|---|---|
| In service since | 2007 | 1996 |
| Region | Illinois | Illinois |
| Blocks assigned | 224 of 786 (28.5%) | 782 of 786 (99.5%) |
| Largest block holder | T-Mobile 19.2% | AT&T 54% |
| Complaints, 28 Sep – 30 Oct 2026 | 591 (#175) | 844 (#84) |
| Rate centers | 24 | 33 |
Block share is allocation by the numbering administrator, not subscribers. Complaint counts cover 28 Sep – 30 Oct 2026 and measure how often each code is spoofed on caller ID.
Frequently asked
What is the difference between area codes 331 and 630?
None geographically – they overlay the same area, so the difference is age and how many numbers are left.
Do I need to dial the area code between 331 and 630?
Yes. Overlay areas use ten-digit dialing for local calls, including between the two codes. Seven digits reaches a recording.
Will a new number be 331 or 630?
Whichever has blocks left – currently 331, at 28.5% allocated against 99.5% for the other. Carriers draw from the code with free blocks, which is why the newer code spreads over time.
Is 331 or 630 more likely to be a spam call?
On the complaint data, 630 appears more often. But spoofing drives those counts, so this is about which code gets imitated, not which numbers are real.
Sources
- 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, 28 Sep – 30 Oct 2026, retrieved Nov 1, 2026
Each code on its own: 331 · 630. All codes in Illinois: Illinois area codes.