Carrier Identification by Phone Number

What is Carrier Identification?

Carrier identification determines which telecommunications company currently serves a phone number. This includes:

• Major wireless carriers — Verizon, AT&T, T-Mobile
• Regional carriers — US Cellular, C Spire, etc.
• MVNOs — Cricket, Metro, Boost, Google Fi, etc.
• VoIP providers — Bandwidth, Twilio, Vonage, etc.
• Landline carriers — Local exchange carriers

Why Carrier Identification Matters

Call Routing

Knowing the terminating carrier helps you:

• Choose least-cost routing paths
• Select direct interconnects for better quality
• Avoid intermediate carriers and associated fees

SMS Delivery

Different carriers have different delivery requirements:

• 10DLC throughput varies by carrier
• Some carriers filter more aggressively
• Direct carrier connections improve deliverability

Billing and Cost Management

Carrier-based billing is common:

• Different rates for different carriers
• On-net vs. off-net pricing
• International vs. domestic carrier charges

Fraud Detection

Carrier type affects risk assessment:

• VoIP numbers are easier to obtain anonymously
• Prepaid carriers may indicate higher risk
• MVNO vs. major carrier patterns

How Carrier Identification Works

There are two approaches to carrier identification:

1. Prefix Lookup (Unreliable)

Originally, the first 6 digits (NPA-NXX) of a phone number identified the carrier. This is no longer reliable because:

• 30%+ of numbers have been ported
• Carriers share prefix blocks
• Number reassignment is common

2. LRN Lookup (Authoritative)

LRN lookup queries the NPAC database for the current carrier:

curl -X POST https://api-service.verirouteintel.io/api/v1/lrn \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "15551234567"}'

# Response
{
  "data": {
    "phone_number": "15551234567",
    "lrn": "5551230000",
    "carrier": "Verizon Wireless"
  },
  "success": true
}

Understanding OCN

The OCN (Operating Company Number) is a 4-character code that uniquely identifies each carrier in the NPAC database. It's more reliable than carrier names, which can vary in formatting.

Example OCNs:

• 6006 — Verizon Wireless
• 6529 — T-Mobile
• 6664 — AT&T Mobility

Learn more about OCN lookup →

Carrier Types

Best Practices

1. Always use LRN lookup for authoritative carrier data
2. Cache results appropriately — carrier changes are infrequent
3. Use OCN for programmatic decisions — carrier names vary
4. Consider carrier type for fraud risk assessment
5. Update stale data — re-lookup numbers periodically