How Twilio Lookup API works


Twilio Lookup API uses mobile-identity signals to verify users and prevent fraud.
It works in the background to look up a phone number and identify real users from those with suspicious behaviors and characteristics, so you can apply additional friction to only the users who present a risk.
With one API, you can look up a number of attributes to prevent potential fraud and undelivered messages.
Get dialed in to fraud signals with phone number lookup
Improve user security, delivery, and conversions in one fell swoop with a single builder-friendly API.
Lookup API features
A complete toolset to protect against fraud with phone number intelligence data, streamline and personalize onboarding, and confirm phone number legitimacy to protect your sender reputation.


Line Type Intelligence
Identify the carrier and phone line type from mobile, landline, fixed VoIP, non-fixed VoIP, toll free, and more to mitigate fake accounts, scrub contact lists, and improve deliverability.
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Formatting and validation
Validate and reformat phone numbers automatically to match national and global dialing standards for optimal deliverability.
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Identity Match
Prevent bots and false account creation. Confirm user identities by matching user-supplied data using a specified phone number against authoritative sources.
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Call forwarding
Expose at-risk numbers with real-time access to the call forwarding status for mobile numbers. Only available in the UK.
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Reassigned number
Check if a phone number has been reassigned since the user's last consent date. Increase user conversion and avoid legal breach by reaching out to the right person.
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SMS Pumping Risk Score
Powered by advanced machine learning models, SMS Pumping Risk Score can effectively identify and flag malicious behavior associated with phone numbers involved in SMS Pumping Fraud.
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Line status
Check if a phone number is active or reachable on its carrier network. Optimize cost and delivery by only sending messages to active contacts.
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Caller name
Identify inbound callers then personalize outreach using the verified caller or business name to improve conversions, security, and customer experience. Only available in the US.
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SIM swap
Detect SIM swap to stop fraud and account takeovers with timestamps and dates of any SIM changes, plus configurable risk tolerance that enables accurate modeling and metrics.
Get started with Twilio Lookup
With a few lines of code, you can start to programmatically get information about phone numbers and who you’re messaging. Reduce undeliverable messages, identify local-friendly number formats, and resolve caller names.
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Stop fraud in its tracks without user signups grinding to a halt
Use Lookup and Verify together for a comprehensive solution that cuts costs, increases OTP conversions, and reduces fraud risk.
cost-per-user and support costs with Verify’s real-time identity signals*
saved by Verify Fraud Guard**
user validations per year*
in user validation time with Lookup Identity Match*
Build now, buy later. Start your free trial.
Reduce your fraud risk and build the secure experience you’ve always wanted. With Twilio Lookup API, you only pay for what you use and there’s no credit card required to start.


* Twilio Accolades Book, page 34, 35
** Total Verify Fraud Guard $62.7M+ in explicit savings from June '22 up to 01 Oct '24