Area code 310 vs 424
310 and 424 are overlay codes: they cover the same ground in California, and a number in one is a local call to the other. 310 is the original, in service since 1991. 424 was added in 2006 because the first was filling up – that is what an overlay is for. Today 310 has 786 of 786 blocks assigned (100.0%) and 424 has 460 of 786 (58.5%), so a new number in the area now almost always comes from 424. In the 33 days to 30 October 2026, 424 drew 631 FTC complaints against 454 for 310 – 163rd and 227th 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
| 310 | 424 | |
|---|---|---|
| In service since | 1991 | 2006 |
| Region | California | California |
| Blocks assigned | 786 of 786 (100%) | 460 of 786 (58.5%) |
| Largest block holder | AT&T 43.6% | T-Mobile 21.1% |
| Complaints, 28 Sep – 30 Oct 2026 | 454 (#227) | 631 (#163) |
| Rate centers | 17 | 16 |
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 310 and 424?
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 310 and 424?
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 310 or 424?
Whichever has blocks left – currently 424, at 58.5% allocated against 100.0% for the other. Carriers draw from the code with free blocks, which is why the newer code spreads over time.
Is 310 or 424 more likely to be a spam call?
On the complaint data, 424 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: 310 · 424. All codes in California: California area codes.