857 Area Code — Boston, MA
Area code 857 serves Boston and 2 other cities in Massachusetts. Local time follows America/New_York. It overlays with 617, so 10-digit dialling is required.
- State
- Massachusetts
- Primary city
- Boston
- Timezone
- America/New_York
- In service since
- 2001
- Type
- Overlay
- Overlay codes
- 617
Overlay of 617
Cities Served by 857
The 857 area code covers 3 cities and communities in Massachusetts.
- Boston
- Cambridge
- Brookline
About Area Code 857
Area code 857 is a North American Numbering Plan (NANP) area code that has been in service since 2001. It is administered by NANPA on behalf of the FCC and serves the Massachusetts region anchored on Boston.
857 is an overlay code, which means it shares its geographic boundaries with one or more existing area codes (617). Overlays are created when a region exhausts the supply of phone numbers in its original area code. Within an overlay region, residents must dial all 10 digits even for local calls, because the same 7-digit number can exist under multiple area codes.
Mobile numbers in 857 are portable: a person who moved away from Boston may still carry a 857 mobile number on their device. If you receive an unexpected call from a 857 number, run it through the reverse lookup tool above for the most accurate, free identification.
If you live or do business in Massachusetts, you may also interact with neighbouring or overlay codes (617). See the related codes section below to explore the rest of Massachusetts.
Other Massachusetts Area Codes
Continue exploring the Massachusetts numbering plan.
857 Area Code FAQ
Where is area code 857?
Area code 857 is located in Massachusetts, primarily serving Boston and surrounding cities including Cambridge, Brookline. The region operates on ET (America/New_York) time.
What state is 857 area code?
857 is a Massachusetts area code. It was put into service in 2001 as an overlay and shares its geographic footprint with overlay code 617.
Is 857 a scam area code?
857 is a legitimate North American area code allocated by NANPA to Massachusetts. Like any geographic area code, scammers sometimes spoof 857 numbers — judge each call by content (urgent demands, unfamiliar transfers) rather than the area code alone. Run the specific number through our reverse lookup if you're unsure.
What time zone does 857 use?
Area code 857 operates on ET (America/New_York). Numbers in this area code follow standard Massachusetts time-zone rules including any daylight-saving transitions for that region.
Can I look up a specific 857 phone number?
Yes. Use the reverse lookup widget above to enter a full 857 number. NumLocation returns the line type (mobile, landline, VoIP), carrier, rate-center city, and any public listings tied to the number — free.
What's the difference between 857 and 617?
857 and 617 cover the same Massachusetts geographic area as overlay codes. Calls between them are local, but you must dial all 10 digits. New phone numbers in this region are assigned from either pool depending on what's available with the carrier at signup.