Tennessee, United States
Central Time
12:23 AM
Area Code
931
State / Province
Tennessee
Country
United States
Time Zone
Central Time
Area code 931 covers 102 cities and communities across Tennessee, based on telephone company rate center data.
Use the E.164 format for clickable phone links (RFC 3966):
<a href="tel:+19315550100">+19315550100</a><a href="tel:+19315550199">+19315550199</a>Look up which exchange in Tennessee a specific 931 number is homed to, and whether its block is wireline or wireless. See what a reverse lookup can establish before relying on the answer.
537 active prefixes in this area code, assigned as 3,686 thousands-blocks — pooling splits one prefix across several carriers, so each block is listed separately with the rate centre it is homed to, its carrier of record, and the switch that serves it.
Showing blocks 1–100 of 3,686
| NPA-NXX | Block | Rate centre | Type | Carrier (OCN) | Switch | LATA | LIR | Dates |
|---|---|---|---|---|---|---|---|---|
| 931-200 | A | Crossville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-201 | 0 | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-201 | 1 | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-201 | 2 | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-201 | 3 | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-201 | 4 | Lawrenceburg | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | NSVMTN177MD | 470 | — | — |
| 931-201 | 5 | Lawrenceburg | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | NSVMTN177MD | 470 | — | — |
| 931-201 | 6 | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-201 | 7 | Lawrenceburg | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | NSVLTNMTY1Z | 470 | — | — |
| 931-201 | 8 | Lawrenceburg | Landline or VoIP | AT&T CORP. (516C) | NSVLTNMTYVY | 470 | — | — |
| 931-201 | 9 | Lawrenceburg | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | NSVLTNMT96Z | 470 | — | — |
| 931-201 | A | Lawrenceburg | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-202 | 0 | Crossville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-202 | 1 | Crossville | Landline or VoIP | CHARTER IP ENABLED SERVICES, LLC (792K) | CKVLTNXAXEX | 470 | — | — |
| 931-202 | 2 | Crossville | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | NSVLTNMTYJZ | 470 | — | — |
| 931-202 | 3 | Crossville | Landline or VoIP | ONVOY, LLC - TN (525E) | CKVLTNXAXDX | 470 | — | — |
| 931-202 | 4 | Crossville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-202 | 5 | Crossville | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | CKVLTNXA6MD | 470 | — | — |
| 931-202 | 6 | Crossville | Landline or VoIP | TELEPORT COMMUNICATIONS AMERICA, LLC - TN (114F) | NSVLTNWMWMD | 470 | — | — |
| 931-202 | 7 | Crossville | Landline or VoIP | CENTURYLINK COMMUNICATIONS, LLC (508J) | NSVLTNMTYUY | 470 | — | — |
| 931-202 | 8 | Crossville | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-202 | 9 | Crossville | Landline or VoIP | ONVOY, LLC - TN (525E) | CKVLTNXAXDX | 470 | — | — |
| 931-202 | A | Crossville | Landline or VoIP | CHARTER IP ENABLED SERVICES, LLC (792K) | CKVLTNXAXEX | 470 | — | — |
| 931-203 | 1 | Sewanee | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-203 | 2 | Sewanee | Landline or VoIP | BEN LOMAND COMMUNICATIONS, INC. (4586) | MC MINNVILLE RURAL | 470 | — | — |
| 931-203 | 3 | Sewanee | Landline or VoIP | BEN LOMAND COMMUNICATIONS, INC. (4586) | MC MINNVILLE RURAL | 470 | — | — |
| 931-203 | 4 | Sewanee | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-203 | 5 | Sewanee | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-203 | 6 | Sewanee | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-203 | 7 | Sewanee | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-203 | 8 | Sewanee | Landline or VoIP | TELNYX LLC (073H) | NSVLTNMTY7Z | 470 | — | — |
| 931-203 | 9 | Sewanee | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-203 | A | Sewanee | Landline or VoIP | TELNYX LLC (073H) | NSVLTNMTY7Z | 470 | — | — |
| 931-205 | A | Shelbyville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-206 | A | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-207 | 0 | Pulaski | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-207 | 1 | Pulaski | Landline or VoIP | PAETEC ITEL, LLC (829J) | NSVLTNMTYXZ | 470 | — | — |
| 931-207 | 2 | Pulaski | Landline or VoIP | PAETEC ITEL, LLC (829J) | NSVLTNMTYXZ | 470 | — | — |
| 931-207 | 3 | Pulaski | Landline or VoIP | PAETEC ITEL, LLC (829J) | NSVLTNMTYXZ | 470 | — | — |
| 931-207 | 4 | Pulaski | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-207 | 6 | Pulaski | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-207 | 7 | Pulaski | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-207 | 8 | Pulaski | Landline or VoIP | PAETEC ITEL, LLC (829J) | NSVLTNMTYXZ | 470 | — | — |
| 931-207 | 9 | Pulaski | Landline or VoIP | METROPCS, INC. (5562) | NSVLTNMTY1Z | 470 | — | — |
| 931-207 | A | Pulaski | Landline or VoIP | PAETEC ITEL, LLC (829J) | NSVLTNMTYXZ | 470 | — | — |
| 931-208 | 0 | McEwen | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | NSVLTNMT96Z | 470 | — | — |
| 931-208 | 1 | McEwen | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-208 | 2 | McEwen | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - TN (124F) | NSVLTNMT96Z | 470 | — | — |
| 931-208 | 3 | McEwen | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-208 | 4 | McEwen | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-208 | 5 | McEwen | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-208 | 6 | McEwen | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-208 | 7 | McEwen | Landline or VoIP | CENTURYLINK COMMUNICATIONS, LLC (508J) | NSVLTNMTYUY | 470 | — | — |
| 931-208 | 8 | McEwen | Landline or VoIP | TELNYX LLC (073H) | NSVNTNGN0MD | 470 | — | — |
| 931-208 | 9 | McEwen | Landline or VoIP | TELNYX LLC (073H) | NSVNTNGN0MD | 470 | — | — |
| 931-208 | A | McEwen | Landline or VoIP | CENTURYLINK COMMUNICATIONS, LLC (508J) | NSVLTNMTYUY | 470 | — | — |
| 931-209 | A | Waverly | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-210 | 0 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | 1 | Crossville | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | CKVLTNXA6MD | 470 | — | — |
| 931-210 | 2 | Crossville | Wireless | POWERTEL NASHVILLE LICENSES, INC. (7476) | CKVLTNXA6MD | 470 | — | — |
| 931-210 | 3 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | 4 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | 5 | Crossville | Landline or VoIP | BEN LOMAND COMMUNICATIONS, INC. (4586) | MC MINNVILLE RURAL | 470 | — | — |
| 931-210 | 6 | Crossville | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | NSVMTN177MD | 470 | — | — |
| 931-210 | 7 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | 8 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | 9 | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-210 | A | Crossville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | CKVLTNXA8MD | 470 | — | — |
| 931-212 | A | Shelbyville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-213 | 0 | Clifton | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-213 | 1 | Clifton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-213 | 2 | Clifton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-213 | 3 | Clifton | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-213 | 4 | Clifton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-213 | 5 | Clifton | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-213 | 6 | Clifton | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-213 | 7 | Clifton | Landline or VoIP | ONVOY, LLC - TN (525E) | NSVLTNMT83Z | 470 | — | — |
| 931-213 | 8 | Clifton | Landline or VoIP | CHARTER IP ENABLED SERVICES, LLC (792K) | LBNNTN071MD | 470 | — | — |
| 931-213 | 9 | Clifton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-213 | A | Clifton | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-214 | 0 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | 1 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | 2 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | 3 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | 4 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | 7 | Gainesboro | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - TN (4806) | NSVMTN177MD | 470 | — | — |
| 931-214 | 9 | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-214 | A | Gainesboro | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-215 | A | Columbia | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-216 | A | Clarksville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-217 | 0 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 1 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 2 | Clarksville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-217 | 3 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 4 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 5 | Clarksville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
| 931-217 | 6 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 7 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 8 | Clarksville | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN (6673) | NSVMTN03DMD | 470 | — | — |
| 931-217 | 9 | Clarksville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - GA (6214) | NSVLTN29GT1 | 470 | — | — |
Block-level assignments from the North American Numbering Plan administrator, via localcallingguide.com.
Assigned Prefixes
537
Assignment Blocks
3,686
Rate Centers
102
Carriers of Record
49
| Type | Blocks | Share |
|---|---|---|
| Landline | 512 | 14% |
| Landline or VoIP | 1,731 | 47% |
| Wireless | 1,443 | 39% |
| Carrier | Blocks |
|---|---|
| ONVOY, LLC - TN | 578 |
| CELLCO PARTNERSHIP DBA VERIZON WIRELESS - TN | 462 |
| NEW CINGULAR WIRELESS PCS, LLC - GA | 428 |
| POWERTEL NASHVILLE LICENSES, INC. | 428 |
| BELLSOUTH TELECOMM INC DBA SOUTH CENTRAL BELL TEL | 334 |
| LEVEL 3 COMMUNICATIONS, LLC - TN | 199 |
| BANDWIDTH.COM CLEC, LLC - TN | 187 |
| CHARTER IP ENABLED SERVICES, LLC | 124 |
| PAETEC ITEL, LLC | 108 |
| METROPCS, INC. | 84 |
| 39 other carriers | 754 |
Carrier of record for each block. Numbers ported to another carrier keep their original block assignment, so this is not a lookup of who serves a given number today.
| Rate Center | Prefixes | Blocks |
|---|---|---|
| Clarksville | 71 | 624 |
| Cookeville | 35 | 193 |
| Columbia | 31 | 221 |
| Shelbyville | 22 | 114 |
| Crossville | 17 | 129 |
| Tullahoma | 17 | 119 |
| Winchester | 15 | 128 |
| Lawrenceburg | 13 | 94 |
| Baxter | 12 | 101 |
| Fayetteville | 11 | 79 |
| Manchester | 11 | 69 |
| Pulaski | 11 | 97 |
| Lewisburg | 9 | 62 |
| McMinnville | 9 | 77 |
| Petersburg | 8 | 51 |
| Hohenwald | 7 | 70 |
| Lynchburg | 7 | 63 |
| Waverly | 7 | 53 |
| Dover | 6 | 52 |
| Sewanee | 6 | 46 |
| Spring Hill | 6 | 55 |
| Centerville | 5 | 51 |
| Gainesboro | 5 | 22 |
| Livingston | 5 | 31 |
| Lyles | 5 | 50 |
| McEwen | 5 | 41 |
| South Oak Grove | 5 | 45 |
| Sparta | 5 | 29 |
| Elkton | 4 | 29 |
| Fredonia | 4 | 35 |
| Lynnville | 4 | 25 |
| McMinnville Rural | 4 | 4 |
| Monterey | 4 | 24 |
| Mount Pleasant | 4 | 35 |
| Sango | 4 | 40 |
| Spencer | 4 | 23 |
| Summertown | 4 | 39 |
| Waynesboro | 4 | 30 |
| Blanche | 3 | 18 |
| Clifton | 3 | 30 |
| Cookeville South | 3 | 13 |
| Culleoka | 3 | 25 |
| Cumberland City | 3 | 26 |
| Cunningham | 3 | 23 |
| Flintville | 3 | 26 |
| Hampshire | 3 | 23 |
| Huntland | 3 | 21 |
| Jamestown | 3 | 5 |
| Normandy | 3 | 22 |
| Palmyra | 3 | 23 |
| Santa Fe | 3 | 23 |
| Wartrace | 3 | 24 |
| Williamsport | 3 | 20 |
| Ardmore | 2 | 5 |
| Beech Grove | 2 | 12 |
| Beersheba | 2 | 3 |
| Belfast | 2 | 3 |
| Bon Decroft | 2 | 3 |
| Celina | 2 | 6 |
| Centertown | 2 | 21 |
| Clarkrange | 2 | 3 |
| Collinwood | 2 | 10 |
| Cornersville | 2 | 13 |
| Dibrell | 2 | 3 |
| Doyle | 2 | 3 |
| Erin | 2 | 11 |
| Estill Springs | 2 | 4 |
| Ethridge | 2 | 5 |
| Hillsboro | 2 | 9 |
| Laager | 2 | 3 |
| Leoma | 2 | 3 |
| Linden | 2 | 14 |
| Loretto | 2 | 3 |
| McBurg | 2 | 3 |
| Minor Hill | 2 | 3 |
| Monteagle | 2 | 3 |
| Moss | 2 | 5 |
| New Johnsonville | 2 | 14 |
| Old Zion | 2 | 4 |
| Pelham | 2 | 7 |
| Pleasant Hill | 2 | 18 |
| Rickman | 2 | 4 |
| Rock Island | 2 | 4 |
| Sparta Rural | 2 | 2 |
| St Joseph | 2 | 4 |
| Tansi | 2 | 18 |
| Tennessee Ridge | 2 | 21 |
| Tracy City | 2 | 5 |
| Viola | 2 | 3 |
| West Vanleer | 2 | 20 |
| Byrdstown | 1 | 1 |
| Chapel Hill | 1 | 1 |
| Crawford | 1 | 10 |
| Five Points | 1 | 1 |
| Flat Creek | 1 | 1 |
| Fosterville (Bedford) | 1 | 1 |
| Granville | 1 | 1 |
| Highland | 1 | 1 |
| Lobelville | 1 | 11 |
| North Springs | 1 | 1 |
| South Guthrie | 1 | 9 |
| Unionville | 1 | 1 |
A rate center is the telephone exchange area a number is homed to. It sets local calling boundaries, and is not the caller's current location.
Area code 931 is a North American Numbering Plan (NANP) telephone area code assigned to Tennessee, United States. It is one of 8 area codes serving Tennessee. As population and demand for phone numbers grew, the region was divided into multiple numbering plan areas to avoid exhausting the available 7-digit number pool.
Yes. 931 is an active North American Numbering Plan (NANP) area code, currently assigned to Tennessee, United States. It is safe to answer or dial calls using this area code.
Area code 931 covers 102 cities and communities in Tennessee, including Ardmore, Baxter, Beech Grove, Beersheba, Belfast, and 97 more localities. This is based on telephone company rate center data — the geographic areas carriers use to determine local calling boundaries and to assign numbers when a business or individual requests a phone number in a specific city.
All numbers in the 931 area code observe Central Time (IANA timezone: America/Chicago). Central Time is UTC−6 in winter (CST) and UTC−5 in summer (CDT). When placing a call to a 931 number from a different time zone, check the current local time above to avoid calling outside of business hours.
From within Tennessee, dial the 7-digit local number directly if calling within the same rate center, or dial 1 + 931 + 7-digit number for long-distance calls within North America. From outside the US or Canada, dial your country's international exit code followed by 1 931 XXX XXXX. The country code for both the United States and Canada in NANP is +1.
Format 931 numbers using E.164 notation as required by RFC 3966: prefix with +1 and omit dashes and parentheses (e.g., +19315550100). This format ensures tel: links work correctly on all mobile browsers and VoIP apps. See the tel: URI formatting guide for complete examples.