The three-digit sequence 671 is a fully legitimate area code within the North American Numbering Plan (NANP).
The definitive answer is that the 671 area code serves the entire island of Guam, a highly strategic and organized unincorporated territory of the United States located in the Western Pacific Ocean. Although geographically far from the mainland, the Federal Communications Commission (FCC) regulates calls to and from Guam as domestic service.
This article details the location, dialing rules, and time zone for the 671 area code, including why all calls to Guam require 10-digit dialing.
Location of Area Code 671: Guam, USA Territory
The 671 area code was introduced in 1997, replacing the previous international country code 671 to lower calling costs for military personnel and residents communicating with the US mainland.
| Detail | Information |
| Area Code: | 671 |
| Location: | Guam (US Territory in the Western Pacific) |
| Capital City: | Hagåtña |
| Time Zone: | Chamorros Standard Time (ChST), which is UTC/GMT +10 hours. |
| Dialing Status: | Domestic (Calls are generally billed as domestic long-distance or included in unlimited plans). |
Time Zone Difference
Guam is one of the first places in the US to see the new day (its motto is “Where America’s Day Begins”).
- Comparison to US Eastern Time (EST): Guam is 15 hours ahead of EST.
- Comparison to US Pacific Time (PST): Guam is 18 hours ahead of PST.
Dialing Rules for Guam (10-Digit Mandatory)
Guam requires 10-digit dialing for all calls, even local ones, due to the nationwide assignment of the 988 National Suicide Prevention Lifeline code.
Calling Guam from the US or Canada
To call any number in the 671 area code from within the NANP, use the 1 + 10-digit format:
- Calling from Guam: Residents calling the US mainland or Canada simply dial 1 + Area Code + 7-digit number, just like a state-to-state call.
Safety and Call Cost Considerations
Calling Costs
For most major US carriers (Verizon, AT&T, T-Mobile), calls to and from Guam (671) are treated as domestic and included in unlimited talk plans.
- Caution: Data usage and text messages while roaming in Guam are governed by the local carriers (such as Docomo Pacific or GTA Teleguam) and are not necessarily included in your T-Mobile or Verizon plan. Check your plan’s roaming policy carefully if traveling to the island.
Scam Alert
The area code 671 is listed as a US territory code commonly spoofed by scammers, often in “one-ring” or “neighbor spoofing” scams.
- Advice: Guam Homeland Security advises residents to be vigilant. If you receive an unexpected call that rings only once, do not call back, and block the number on your device.
Frequently Asked Questions (FAQ)
What is the major city in the 671 area code?
The largest city is Dededo, while the capital is Hagåtña (formerly Agana). The entire island uses the 671 area code.
Does the 671 area code have an overlay?
No. Area code 671 is the sole area code for Guam. The mandatory 10-digit dialing was implemented in 2021 solely to accommodate the 988 code, not due to an overlay.
Is Guam the same as the Northern Mariana Islands?
No. The Northern Mariana Islands (Saipan, Tinian, Rota) are separate US territories and use the 670 area code.
Conclusion
The 671 area code is the domestic US code for Guam, requiring 1 + 671 + 7-digit dialing. While calls are treated as domestic, the 15-hour time difference and local scam warnings make it prudent to confirm the identity of any unexpected caller from this Western Pacific location.
