Area code 331 covers Aurora and surrounding communities in Illinois.
Updated 8 October 2026
Area code 331 is in Illinois, shown here with Aurora marked.
Now in Aurora
Central Time · UTC−6, UTC−5 in summer
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Typical business hours, 9 to 5 Monday to Friday.
Typical business hours, 9 to 5 Monday to Friday, shown as the blue arc. A guide to when a real Aurora office is likely to answer. It says nothing about who called you.
Source: North American Numbering Plan Administrator, retrieved 8 October 2026.
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Is area code 331 a scam?
No. Area code 331 is a legitimate area code serving Aurora since 2007. Scammers spoof caller ID to display 331 numbers, which is why complaints exist against a code that is itself genuine.
Neighbour spoofing is the reason a local-looking number is not a guarantee. A caller anywhere in the world can display a 331 number, and the number they display may belong to a real business in Aurora that has nothing to do with the call.
The callerAnywhere in the worldSets the caller ID their equipment sends.
What is displayed(331) 888-1773May belong to a real Aurora business.
Your phoneLooks localA nearby code and prefix make you likelier to answer.
285Area code 331 had 285 different numbers reported for spam calls in the 30 days to 8 October 2026.
262ndArea code 331 ranks 262nd of 331 US geographic area codes by spam complaint volume.
58%Of the 340 complaints about area code 331 in the 30 days to 8 October 2026, 58% were reported as a recorded message or robocall.
30%The most reported subject on area code 331 is reducing your debt (credit cards, mortgage, student loans), appearing in 30% of its complaints in the 30 days to 8 October 2026.
Why am I getting text messages from area code 331?
Texts from 331 numbers follow the same pattern as calls — mostly local businesses and services. Treat any text asking for payment or credentials as suspect regardless of the code.
The common patterns are a wrong-number opener that turns into conversation, an unsolicited job offer, and a crypto or investment tip. Do not reply, do not follow the link, and forward the message to 7726 (SPAM) to report it to your carrier.
Pattern 1Wrong-number openerTurns into conversation.
Pattern 2Unsolicited job offerDo not reply, do not follow the link.
Pattern 3Crypto or investment tipTreat any payment ask as suspect.
Report it7726Forward the message. It spells SPAM on a keypad.
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Area codes that overlay 331
Area code 331 shares its geographic footprint with one other code: 630. Overlays are laid over an existing area rather than splitting it, so all local calls require the full ten-digit number.
Aurora is the second-largest city in Illinois and the western anchor of Chicago's suburban economy. Its industrial base runs to manufacturing, logistics, and healthcare, with the Hollywood Casino and the restored Paramount Theatre pulling entertainment spending into a downtown that has been rebuilding itself along the Fox River. The corridor gained area code 331 in 2007 as an overlay on 630, covering Aurora, Naperville, and the DuPage County corridor, one of the most commercially dense suburban stretches in the Midwest. A 331 number is simply the newer issue in the same territory.
Who lives in the 331 region
The area's households are notably well off for a manufacturing city. DataUSA recorded 179,898 residents in Aurora in 2024, with a median household income of $93,633 and a poverty rate of 9.52 percent. Employment stood at 95,533. The city is one of the most diverse in Illinois, with a large Spanish-speaking population, and businesses in Aurora, Illinois routinely serve customers in both English and Spanish. Corporate offices and distribution centers along the Interstate 88 corridor add a white-collar and logistics layer to the older industrial base.
What a 331 number signals to a caller
Callers familiar with the region describe suburban Chicago phone behavior as brisk. People answer for numbers they recognize, and the 630 and 331 codes are treated as one and the same by locals, who have dialed ten digits since the overlay took effect. Business calls placed during the workday to this corridor reach office workers and shop floors on Central Time schedules, and callers who state their business quickly are generally received better than those who open with pleasantries.
Area code 331 serves Aurora and surrounding communities in Illinois. It is in the Central Time zone.
What state is area code 331 in?
Area code 331 is in Illinois. It is not in Detroit — those are area code 313.
Is area code 331 toll free?
No. Area code 331 is a geographic area code serving Aurora, Illinois. The toll-free codes are 800, 833, 844, 855, 866, 877, 888, and a call to a 331 number is charged at your normal rate.
Why am I getting calls from 331?
Calls displaying a 331 number come from businesses and individuals in the Aurora area, and from anywhere at all when caller ID is spoofed to look local. 285 331 numbers were reported to the FTC in the 30 days to 8 October 2026.
How do I block calls from area code 331?
Both iOS and Android can silence calls from unknown numbers, and every major US carrier offers free call-blocking. Blocking the whole of area code 331 is rarely worth it, because spoofed numbers change constantly and you would lose legitimate calls from Aurora.