Maryland, United States
Eastern Time
1:23 AM
Area Code
410
State / Province
Maryland
Country
United States
Time Zone
Eastern Time
Area code 410 covers 103 cities and communities across Maryland, based on telephone company rate center data.
Use the E.164 format for clickable phone links (RFC 3966):
<a href="tel:+14105550100">+14105550100</a><a href="tel:+14105550199">+14105550199</a>Look up which exchange in Maryland a specific 410 number is homed to, and whether its block is wireline or wireless. See what a reverse lookup can establish before relying on the answer.
786 active prefixes in this area code, assigned as 4,526 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 4,526
| NPA-NXX | Block | Rate centre | Type | Carrier (OCN) | Switch | LATA | LIR | Dates |
|---|---|---|---|---|---|---|---|---|
| 410-200 | 0 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 1 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 2 | Easton | Landline or VoIP | IDT AMERICA, CORP. - MD (228C) | ESTNMDESMMD | 242 | — | — |
| 410-200 | 3 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 4 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 5 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 6 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 7 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 8 | Easton | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-200 | 9 | Easton | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MD (7228) | ESTNMDES5MD | 242 | — | — |
| 410-200 | A | Easton | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MD (7228) | ESTNMDES5MD | 242 | — | — |
| 410-201 | A | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | ODDBALL CODES | 238 | — | — |
| 410-202 | 0 | Salisbury | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - MD (6119) | SLBRMDSBXFX | 242 | — | — |
| 410-202 | 1 | Salisbury | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | SLBRMDSCXMD | 242 | — | — |
| 410-202 | 2 | Salisbury | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - MD (6119) | SLBRMDSBXFX | 242 | — | — |
| 410-202 | 3 | Salisbury | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MD (7228) | ESTNMDES5MD | 242 | — | — |
| 410-202 | 4 | Salisbury | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | SLBRMDSCXMD | 242 | — | — |
| 410-202 | 5 | Salisbury | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | SLBRMDSCXMD | 242 | — | — |
| 410-202 | 6 | Salisbury | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-202 | 7 | Salisbury | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | SLBRMDSCXMD | 242 | — | — |
| 410-202 | 8 | Salisbury | Landline or VoIP | LEVEL 3 COMMUNICATIONS, LLC - MD (6119) | SLBRMDSBXFX | 242 | — | — |
| 410-202 | 9 | Salisbury | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-202 | A | Salisbury | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | ESTNMDESQMD | 242 | — | — |
| 410-203 | A | Ellicott City | Landline | VERIZON MARYLAND, INC. (9212) | ELLICOTT CITY | 238 | — | — |
| 410-204 | 0 | Arbutus | Landline or VoIP | BARR TELL USA, INC. (964H) | BLTQMD012MD | 238 | — | — |
| 410-204 | 1 | Arbutus | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-204 | 2 | Arbutus | Landline or VoIP | ONVOY, LLC - MD (876D) | BLTMMDCH42Z | 238 | — | — |
| 410-204 | 3 | Arbutus | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-204 | 4 | Arbutus | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-204 | 5 | Arbutus | Landline or VoIP | ONVOY, LLC - MD (876D) | BLTMMDCH42Z | 238 | — | — |
| 410-204 | 6 | Arbutus | Landline | VERIZON MARYLAND, INC. (9212) | ARBUTUS | 238 | — | — |
| 410-204 | 7 | Arbutus | Landline | VERIZON MARYLAND, INC. (9212) | ARBUTUS | 238 | — | — |
| 410-204 | 8 | Arbutus | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | BLTMMDCHXFX | 238 | — | — |
| 410-204 | 9 | Arbutus | Landline or VoIP | IP HORIZON LLC (515J) | — | 238 | — | — |
| 410-204 | A | Arbutus | Landline | VERIZON MARYLAND, INC. (9212) | ARBUTUS | 238 | — | — |
| 410-205 | 0 | Pikesville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-205 | 1 | Pikesville | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-205 | 2 | Pikesville | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC (7229) | BLTMMDCHXNX | 238 | — | — |
| 410-205 | 3 | Pikesville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-205 | 4 | Pikesville | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-205 | 5 | Pikesville | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-205 | 6 | Pikesville | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-205 | 7 | Pikesville | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | BLTMMDCHXFX | 238 | — | — |
| 410-205 | 8 | Pikesville | Landline or VoIP | PAETEC ITEL, LLC (829J) | PIVLMDPKXEX | 238 | — | — |
| 410-205 | 9 | Pikesville | Landline or VoIP | BANDWIDTH.COM CLEC, LLC - MD (071F) | BLTMMDCH45Z | 238 | — | — |
| 410-205 | A | Pikesville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-206 | A | Catonsville | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-207 | A | Baltimore | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | BLTOMDKHBMD | 238 | — | — |
| 410-208 | 0 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 1 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 2 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 3 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 4 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 5 | Berlin | Landline or VoIP | ONVOY, LLC - MD (876D) | SLBRMDSBXVX | 242 | — | — |
| 410-208 | 6 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | 7 | Berlin | Landline or VoIP | ONVOY, LLC - MD (876D) | SLBRMDSBXVX | 242 | — | — |
| 410-208 | 8 | Berlin | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | SLBRMDSCXLX | 242 | — | — |
| 410-208 | 9 | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-208 | A | Berlin | Landline | VERIZON MARYLAND, INC. (9212) | OCEAN PINES | 242 | — | — |
| 410-209 | 0 | Baltimore | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-209 | 1 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 2 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 3 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 4 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 5 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 6 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 7 | Baltimore | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-209 | 8 | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-209 | 9 | Baltimore | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-209 | A | Baltimore | Landline | VERIZON MARYLAND, INC. (9212) | BALTIMORE CHARLES STREET | 238 | — | — |
| 410-210 | 0 | Glen Burnie | Wireless | ONVOY SPECTRUM, LLC (624H) | BLTMMDCHXUX | 238 | — | — |
| 410-210 | 1 | Glen Burnie | Wireless | ONVOY SPECTRUM, LLC (624H) | BLTMMDCHXUX | 238 | — | — |
| 410-210 | 2 | Glen Burnie | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | BLTOMDKHBMD | 238 | — | — |
| 410-210 | 3 | Glen Burnie | Wireless | ONVOY SPECTRUM, LLC (624H) | BLTMMDCHXUX | 238 | — | — |
| 410-210 | 4 | Glen Burnie | Landline or VoIP | PEERLESS NETWORK OF MARYLAND, LLC (568G) | BALTIMORE | 238 | — | — |
| 410-210 | 5 | Glen Burnie | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-210 | 6 | Glen Burnie | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-210 | 7 | Glen Burnie | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-210 | 8 | Glen Burnie | Wireless | ONVOY SPECTRUM, LLC (624H) | BLTMMDCHXUX | 238 | — | — |
| 410-210 | 9 | Glen Burnie | Wireless | NEW CINGULAR WIRELESS PCS, LLC - DC (4036) | CLMAMDORAMD | 238 | — | — |
| 410-210 | A | Glen Burnie | Wireless | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD (6395) | BLTOMDKHBMD | 238 | — | — |
| 410-212 | 0 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 1 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 2 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 3 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 4 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 5 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 6 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 7 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 8 | Annapolis | Landline or VoIP | METROPCS, INC. (5562) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | 9 | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-212 | A | Annapolis | Wireless | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC (6855) | BLTMMDCH40Z | 238 | — | — |
| 410-213 | 0 | Ocean City | Landline | VERIZON MARYLAND, INC. (9212) | WEST OCEAN CITY | 242 | — | — |
| 410-213 | 1 | Ocean City | Landline | VERIZON MARYLAND, INC. (9212) | WEST OCEAN CITY | 242 | — | — |
| 410-213 | 2 | Ocean City | Landline | VERIZON MARYLAND, INC. (9212) | WEST OCEAN CITY | 242 | — | — |
| 410-213 | 3 | Ocean City | Landline or VoIP | ONVOY, LLC - MD (876D) | SLBRMDSBXVX | 242 | — | — |
| 410-213 | 4 | Ocean City | Landline or VoIP | COMCAST IP PHONE, LLC (318J) | SLBRMDSBXLX | 242 | — | — |
| 410-213 | 5 | Ocean City | Landline or VoIP | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MD (7228) | ESTNMDES5MD | 242 | — | — |
| 410-213 | 6 | Ocean City | Landline or VoIP | TERRA NOVA TELECOM INC. (145J) | — | 242 | — | — |
| 410-213 | 7 | Ocean City | Landline | VERIZON MARYLAND, INC. (9212) | WEST OCEAN CITY | 242 | — | — |
Block-level assignments from the North American Numbering Plan administrator, via localcallingguide.com.
Assigned Prefixes
786
Assignment Blocks
4,526
Rate Centers
103
Carriers of Record
38
| Type | Blocks | Share |
|---|---|---|
| Landline | 1,868 | 41% |
| Landline or VoIP | 1,769 | 39% |
| Wireless | 889 | 20% |
| Carrier | Blocks |
|---|---|
| VERIZON MARYLAND, INC. | 1,867 |
| OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC | 332 |
| NEW CINGULAR WIRELESS PCS, LLC - DC | 307 |
| ONVOY, LLC - MD | 245 |
| MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MD | 196 |
| CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD | 191 |
| BANDWIDTH.COM CLEC, LLC - MD | 160 |
| PAETEC ITEL, LLC | 157 |
| LEVEL 3 COMMUNICATIONS, LLC - MD | 151 |
| CORE COMMUNICATIONS, INC.- MD | 141 |
| 28 other carriers | 779 |
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 |
|---|---|---|
| Baltimore | 192 | 912 |
| Towson | 53 | 252 |
| Annapolis | 36 | 196 |
| Catonsville | 35 | 135 |
| Glen Burnie | 29 | 219 |
| Salisbury | 24 | 94 |
| Waterloo (Washington DC LATA) | 23 | 93 |
| Columbia | 20 | 60 |
| Elkridge | 20 | 100 |
| Pikesville | 19 | 109 |
| Severna Park | 18 | 168 |
| Cockeysville | 16 | 116 |
| Ellicott City | 16 | 96 |
| Fork | 16 | 130 |
| Easton | 14 | 103 |
| Parkville | 14 | 63 |
| Woodlawn | 12 | 42 |
| Arbutus | 10 | 79 |
| Bel Air | 10 | 60 |
| Essex | 10 | 50 |
| Severn | 9 | 49 |
| Edgewood | 8 | 68 |
| Westminster | 8 | 28 |
| Elkton | 7 | 47 |
| Ocean City | 7 | 37 |
| Reisterstown | 7 | 37 |
| Odenton | 6 | 56 |
| Prince Frederick | 6 | 16 |
| Sykesville | 6 | 46 |
| Aberdeen | 5 | 35 |
| Armiger-Gibson Island | 5 | 15 |
| Berlin | 5 | 45 |
| Brooklyn Park-Linthicum | 5 | 35 |
| Dundalk | 5 | 15 |
| Fallston | 5 | 25 |
| Randallstown | 5 | 15 |
| Cambridge | 4 | 24 |
| Chestertown | 4 | 24 |
| Solomons | 4 | 34 |
| Centreville | 3 | 23 |
| Chase | 3 | 23 |
| Crofton | 3 | 13 |
| Sparrows Point | 3 | 13 |
| West River | 3 | 23 |
| Churchville | 2 | 22 |
| Havre de Grace | 2 | 12 |
| Millersville | 2 | 12 |
| North Beach | 2 | 12 |
| North East | 2 | 12 |
| Perryville | 2 | 22 |
| Princess Anne | 2 | 12 |
| Queenstown | 2 | 22 |
| Rising Sun | 2 | 12 |
| Sherwood Forest | 2 | 22 |
| Sparks-Glencoe | 2 | 22 |
| Stevensville | 2 | 12 |
| Trappe | 2 | 22 |
| Waterloo | 2 | 11 |
| Bishopville | 1 | 11 |
| Cardiff | 1 | 11 |
| Cecilton | 1 | 11 |
| Chesapeake City | 1 | 11 |
| Church Hill | 1 | 8 |
| Crisfield | 1 | 11 |
| Darlington | 1 | 11 |
| Deal Island | 1 | 8 |
| Delmar | 1 | 11 |
| Denton | 1 | 11 |
| Federalsburg | 1 | 11 |
| Galena | 1 | 11 |
| Glenwood | 1 | 11 |
| Greensboro | 1 | 11 |
| Hampstead | 1 | 11 |
| Hillsboro | 1 | 11 |
| Hurlock | 1 | 11 |
| Jarrettsville | 1 | 11 |
| Jarrettsville 941 | 1 | 11 |
| Marion | 1 | 11 |
| Millington | 1 | 11 |
| Nanticoke | 1 | 11 |
| New Windsor | 1 | 11 |
| Oxford | 1 | 11 |
| Parkton | 1 | 11 |
| Pocomoke | 1 | 11 |
| Port Deposit | 1 | 11 |
| Preston | 1 | 10 |
| Ridgely | 1 | 11 |
| Rock Hall | 1 | 10 |
| Sharptown | 1 | 11 |
| Silver Run | 1 | 11 |
| Smith Island | 1 | 8 |
| Snow Hill | 1 | 11 |
| St Michaels | 1 | 11 |
| Still Pond | 1 | 11 |
| Sudlersville | 1 | 9 |
| Taneytown | 1 | 11 |
| Tilghman | 1 | 9 |
| Union Bridge | 1 | 11 |
| Vienna | 1 | 11 |
| Warwick | 1 | 9 |
| Willards | 1 | 11 |
| Wingate | 1 | 9 |
| Worthington | 1 | 11 |
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 410 is a North American Numbering Plan (NANP) telephone area code assigned to Maryland, United States. It is one of 6 area codes serving Maryland. 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. 410 is an active North American Numbering Plan (NANP) area code, currently assigned to Maryland, United States. It is safe to answer or dial calls using this area code.
Area code 410 covers 103 cities and communities in Maryland, including Aberdeen, Annapolis, Arbutus, Armiger-Gibson Island, Baltimore, and 98 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 410 area code observe Eastern Time (IANA timezone: America/New_York). Eastern Time is UTC−5 in winter (EST) and UTC−4 in summer (EDT). When placing a call to a 410 number from a different time zone, check the current local time above to avoid calling outside of business hours.
From within Maryland, dial the 7-digit local number directly if calling within the same rate center, or dial 1 + 410 + 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 1 410 XXX XXXX. The country code for both the United States and Canada in NANP is +1.
Format 410 numbers using E.164 notation as required by RFC 3966: prefix with +1 and omit dashes and parentheses (e.g., +14105550100). This format ensures tel: links work correctly on all mobile browsers and VoIP apps. See the tel: URI formatting guide for complete examples.