Area code 831 – California
831 has served California since 1998, split from 408. 406 of its 786 number blocks are allocated (52%). AT&T is the largest holder with 42.9% of blocks, ahead of Other CLEC / VoIP at 17.0%. FTC complaints naming a 831 caller ID totalled 458 in the 33 days to 30 October 2026 (225th of 422 ranked codes).
- State
- California
- In service since
- 1998
- Time zone
- Pacific
- Shares area with
- No overlay
Who holds 831 number blocks
Share of the 406 assigned NXX blocks (51.7% of the 786 possible), across 45 carriers. This is share of number blocks, not of subscribers.
- AT&T42.9%
- Other CLEC / VoIP13.5%
- Verizon10.1%
- Onvoy7.6%
- Lumen7.4%
- T-Mobile6.4%
- TPx2.7%
- Bandwidth2.7%
- Peerless2%
- Charter2%
- Telnyx0.7%
- Comcast0.7%
- Vonage0.2%
- Dish0.2%
- VoIP Innovations0.2%
- Twilio0.2%
- 8x80.2%
Spam complaints naming 831
FTC Do Not Call complaints where the caller ID was a 831 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 831
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 24.
Timeline
- 1998 831 goes into service, split from or overlaid on 408.
More about 831
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 831
What state is area code 831?
California.
Is a call from 831 a scam?
Not by itself. 831 drew 458 FTC complaints in the 33 days to 30 October 2026, 225th 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 831 numbers?
AT&T holds the largest share of assigned number blocks at 42.9%. 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 831?
No. NANPA records 831 as 7-digit dialing for local calls.
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: “7D”. Reviewed by the data desk. Spotted an error? Request a correction.