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Number Lookup —
Phone Number Validation API for International SMS Routing

Validate carrier, country, reachability, portability, and roaming status before you send — reducing wasted traffic and improving delivery rates across 200+ countries.

Request Lookup access →View API
200+
Countries
HLR
Real-time query
NPDB
Korea · Japan
Pre-send
Validation

What is phone number lookup?

Phone Number Lookup verifies whether a mobile number is valid, active, reachable, and associated with the correct carrier before sending authentication or business messages.

Businesses use phone number lookup to improve delivery rates, reduce messaging costs, prevent fraud, and optimize customer verification.

Why use phone number lookup?

Improve delivery rates
Reach valid and reachable numbers only.
Reduce messaging costs
Avoid sending to invalid or inactive numbers.
Prevent fraud and abuse
Verify numbers and reduce risk of fraud or misuse.
Optimize routing
Route messages via the best carrier for higher success.
Enhance customer experience
Ensure accurate OTPs and critical notifications are delivered.

How number lookup works

SureM Number Lookup queries the HLR (Home Location Register) — the central database maintained by mobile carriers that stores subscriber information including current network, roaming status, and handset availability. Real-time HLR queries return subscriber status within seconds, enabling pre-send filtering before SMS traffic is dispatched.

1. Customer
Your customer
initiates a request
2. Phone number
Phone number
is submitted
3. SureM Lookup
Real-time HLR query
to mobile carriers
4. Carrier validation
Validate carrier, network,
roaming status, and
handset availability
5. OTP
Send OTP via SMS
or Voice
6. Login
Customer logs in
successfully
All lookups are completed in real time within seconds for maximum accuracy and delivery success.

Perfect for authentication

Validate the phone number before sending an OTP to improve verification success.

1. Validate number
Check if the number is
valid, active, and reachable
2. Send SMS OTP
Send OTP via SMS to
the validated number
3. Fallback to Voice OTP
If SMS fails, automatically
fallback to Voice OTP
4. Verified
Customer is verified
successfully

Prevent fraud before it happens

Lookup helps businesses identify risky numbers before messaging.

Invalid numbers
Disconnected or
non-existent numbers
Deactivated numbers
Inactive or deactivated
accounts
Suspicious registrations
Recently created or
unusual registrations
Carrier mismatches
Number not matching
the expected carrier
Fake accounts
High-risk or fraudulent
accounts

Reduce SMS cost

Filtering invalid numbers before sending prevents wasted traffic.

Without lookup
Invalid number
SMS sent
Cost incurred
Delivery fails
You pay for messages that don’t reach.
With lookup
Invalid number detected
No SMS sent
Cost saved
Delivery success improved
Save costs. Improve delivery. Increase ROI.

API request & response

Simple API request returns real-time number portability status.

Request
POST https://api.surem.net/v2/lookup
{
"numbers": ["+819012345678", "+8613912345678"]
}
Response
{
"results": [
{
"number": "+819012345678",
"country": "JP",
"carrier": "NTT Docomo",
"type": "mobile",
"status": "active",
"ported": false,
"roaming": false
}
]
}
iActual endpoint and response structure — dev team to confirm.

Mobile number portability (MNP)

When a subscriber moves their number from one carrier to another (e.g., from SKT to KT), their number is flagged as ported in the carrier’s NPDB. Without portability-aware routing, SMS sent to a ported number may be routed to the original carrier and fail. SureM Lookup checks NPDB portability status so traffic is routed to the subscriber’s current carrier.

SKT to KT porting via NPDB

Coverage

Coverage varies by lookup type.

Lookup typeCoverage
Carrier / country lookup🌐200+ countries
NPDB (Number Portability Database)🇰🇷Korea and Japan

Actual coverage — dev team to confirm.

Lookup types

Carrier LookupHLR LookupNumber ValidationReachability CheckLine Type DetectionCountry DetectionRoaming Status

Lookup vs validation

CapabilityLookupValidation
Carrier
Active number
Reachability
Formatting

Use cases

Banking
Customer verification.
FinTech
KYC.
E-commerce
Fake account prevention.
Healthcare
Patient verification.
Travel
Booking validation.
SaaS
User registration.
Gaming
Account protection.
Delivery
Customer validation.

Frequently asked questions

What is phone number lookup?
Phone Number Lookup verifies whether a mobile number is valid, active, reachable, and associated with the correct carrier before sending authentication or business messages. Businesses use it to improve delivery rates, reduce messaging costs, prevent fraud, and optimize customer verification.
How does number lookup work technically?
SureM queries the HLR (Home Location Register) maintained by mobile carriers in real time. The query returns subscriber status — current network, roaming state, and handset availability — within seconds, enabling pre-send filtering before SMS traffic is dispatched.
What is mobile number portability (MNP)?
MNP lets a subscriber keep their number when switching carriers. The number is flagged as ported in the NPDB. SureM Lookup checks NPDB portability status so messages route to the subscriber’s current carrier instead of the original one.
Which countries are covered?
Carrier and country lookup covers 200+ countries. NPDB portability lookup currently covers Korea and Japan. Actual coverage is confirmed by the SureM team based on your routing needs.
How does lookup reduce SMS costs?
By filtering invalid, inactive, or unreachable numbers before sending, lookup prevents wasted traffic — you stop paying for messages that can never be delivered, which lowers cost and raises overall delivery success and ROI.
Related
SMS ↗Voice OTP ↗SMPP ↗SMS API ↗Contact ↗

Validate numbers before you send

Talk with SureM about pre-send lookup, HLR queries, and NPDB portability routing.

Request Lookup access →intlsales@surem.com

SureM is a Korea-based business messaging infrastructure provider with 26 years of experience. SureM helps global messaging partners, foreign-invested companies in Korea, and Korean enterprises deliver SMS, LMS, MMS, RCS, Kakao, WhatsApp Business, Voice OTP, and international messages through reliable local network connectivity and global messaging reach.