Area code
773
773 is a United States area code. Under the North American Numbering Plan it belongs to Illinois, which has 17 area codes in total.
Validate a number in 773
Paste a full number and the tool checks it against the numbering plan. It returns the standard formats, the line type the plan assigns and the area code region.
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Area code 773 at a glance
NANPA lists 785 central office codes (prefixes) in use in area code 773, held by 21 holders across 11 rate centers.
| Fact | Value |
|---|---|
| In service since | 1996-10-12 |
| Time zone | Central (C) |
| Assigned overlays | 872 (2009-11-07) |
| Prefixes in use | 785 |
| Pooled prefixes | 484 (62%) |
| Rate centers | 11 |
| Companies holding prefixes | 21 |
| Assignment dates on file | 2001-02-02 to 2025-10-15 (228 prefixes) |
Rate centers in area code 773
| Rate center | Prefixes | Share |
|---|---|---|
| CHICGOZN03 | 170 | 22% |
| CHICGOZN01 | 124 | 16% |
| CHICGOZN02 | 79 | 10% |
| CHICGOZN07 | 78 | 10% |
| CHICGOZN04 | 75 | 10% |
| CHICGOZN10 | 72 | 9% |
| CHICGOZN06 | 56 | 7% |
| CHICGOZN08 | 45 | 6% |
| 3 other rate centers | 86 | 11% |
Who holds the prefixes in 773
Illinois Bell Tel holds the most prefixes, 257 (33%). 62% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
| Holder | Prefixes | Share |
|---|---|---|
| Illinois Bell Tel | 257 | 33% |
| T-Mobile USA | 169 | 22% |
| New Cingular Wireless PCS | 84 | 11% |
| Verizon Wireless | 59 | 8% |
| Mcimetro Access Transmission Services | 46 | 6% |
| Level 3 Communications | 36 | 5% |
| 15 other carriers | 134 | 17% |
A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company. Find which carrier a number is on, or browse the prefix holders.
History of area code 773
- 1947-01-01 Area code 312, named as the parent of 773 in the NANPA report, was in service.
- 1996-10-12 Area code 773 went into service.
Complaints on file for 773 numbers
3,581 FCC complaints are on file for 2,494 numbers in 773, most often filed as "Unwanted Calls". These are unverified consumer reports.
| Year of latest complaint | Numbers |
|---|---|
| 2023 | 120 |
| 2024 | 137 |
| 2025 | 102 |
Other area codes in Illinois
Illinois is one state with 17 area codes in the NANPA table. 773 is one of them.
Next to 773 in the numbering table
These are the codes just before and after 773 when all are sorted by number. They are neighbours on the list, not necessarily on the map.
What the area code does and does not tell you
A number that starts with 773 was first assigned in Illinois. That is a fact about where the number began, and it is a useful hint when you check a form entry, for example a billing address in Illinois next to a 773 phone number.
It does not show where the person is today. A number stays with its owner after a move or a change of provider (number portability), and mobile numbers travel with the handset. The area code also cannot tell you whether the line is active, who the carrier is, or whether the number is mobile or fixed: the plan shares those ranges. Read more about the area code, the numbering plan and line type.
Check numbers in bulk with the API
| Product | Credits | Docs |
|---|---|---|
| Phone Numbering-Plan Validation | 1 credit per valid number | API docs |
| Phone Intelligence (carrier and line status) | 1 credit per check (invalid numbers outside the US and Canada are free) | Product page |
Questions about area code 773
Where is area code 773?
NANPA assigns area code 773 to Illinois, United States.
In which state does area code 773 sit?
Illinois. 773 is one of 17 area codes the NANPA table assigns to the state.
Who owns area code 773?
NANPA assigns area codes. Within 773, Illinois Bell Tel holds the most prefixes, 257 prefixes or 33%.
Which time zone does 773 use?
The NANPA NPA report lists the time zone for 773 as Central (C).
What year did 773 enter service?
The NANPA NPA report gives an in-service date of 1996-10-12, so 773 has been in use since 1996.
Does area code 773 have an overlay?
Yes. 872 (in service 2009-11-07) shares the same area with 773, so numbers from all of them are local to each other.
How many prefixes does area code 773 have?
NANPA's report dated 2026-10-17 lists 785 prefixes in service in 773, spread over 11 rate centers and 21 holders.
Are there complaints about 773 numbers?
The FCC data on file has 3,581 complaints for 2,494 numbers in 773. They are unverified consumer reports. A number with no complaints on file is not proven safe.
Area code assignments: North American Numbering Plan Administrator NPA report, file dated 10/17/2026, retrieved 2026-10-17. Source file. New codes are assigned several times a year. Prefixes, rate centers, holders, time zone, in-service date and overlays: NANPA central office code report dated 2026-10-17 and NPA report dated 2026-10-18. Complaints: FCC consumer complaints open data, fetched 2026-10-17. ZIP code places: Postal code places and coordinates: GeoNames (geonames.org), licensed CC BY 4.0.