Twilio Lookup API: Intelligent Authentication

Summary

Web page for Twilio Lookup API, which the page describes as using mobile-identity signals to verify users and prevent fraud by looking up phone number attributes. It lists uses including improving SMS and voice deliverability, fraud prevention across the customer journey, enriching risk models and raising conversion rates. Customer examples include Resy, with 35 million registered users and 21 million messages sent monthly, and Tradier, which reduced validation times by around 90%. Persona reports an estimated $300,000 in fraud losses before Lookup, and Choco reports 10,000+ suppliers in its ecosystem. The page states that users only pay for what they use and that no credit card is required to start.

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Twilio Lookup API

Intelligent authentication so smooth, users will think they skipped a step

Lookup API uses mobile-based signals to provide smooth and robust protection for digital platforms and users, minimizing fraudulent activities without compromising the experience.

Start for free View pricing

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.

Explore docs

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.

Increase SMS message and voice deliverability

Improve contact rates by using mobile-based signals that give accurate contact information such as formatting, line type, line status, and active consent. When you can communicate more effectively with end users, you can also lower delivery costs.

Resy securely verifies customers and delivers verification codes to confirm their identities, keep their accounts secure, and maintain on-time message delivery.

35 million

registered users

21 million

messages sent monthly

Read Resy’s story

Fraud prevention across the customer journey

Prevent fraudulent schemes like fake account creation, bot attacks, SIM swap, promo abuse, SMS Pumping fraud, and other types of fraud from damaging your platform at key touchpoints of the customer journey.

Learn about fraud prevention

Tradier increased the number of user verification sources it uses while also improving its user experience. By filtering out real unique users with Lookup Identity Match and flagging suspicious ones, Tradier reduced validation times by around 90%.

Read Tradier’s story

Enrich data and risk models with mobile signals

Include key data such as risk scoring and phone number attributes in fraud risk models. This enriches the user information you have in your fraud data pipeline to identify fraudsters and assess user risk.

After an estimated $300,000 in losses from artificially inflated SMS traffic over the course of three years, Persona needed better tools to prevent SMS pumping fraud by identifying fraud behavior.

6 months

without SMS pumping traffic spikes

$300,000

estimated fraud losses before Lookup

Read Persona’s story

Raise conversion rates and boost revenue

Leverage authoritative data and mobile based signals to fast track time to conversion and boost revenue.

Choco uses the Lookup API to validate phone numbers when processing orders from restaurants and food service operators with suppliers. This allows them to complete orders securely, easily, and efficiently.

2+

hours a week saved with ordering

10,000+

suppliers in Choco’s ecosystem

Read Choco’s story

Twilio 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.

New

Device Fingerprinting

Pair Lookup with device intelligence to stop fraudulent users even earlier. For deep risk analysis before traffic even reaches your login flow, combine Lookup with Stytch by Twilio Device Fingerprinting.

Learn about Device Fingerprinting

- Formatting and validation Validate and reformat phone numbers automatically to match national and global dialing standards for optimal deliverability.
- Identity Match Prevent bots and false account creation. Confirm user identities by matching user-supplied data using a specified phone number against authoritative sources.
- Call forwarding Expose at-risk numbers with real-time access to the call forwarding status for mobile numbers. Only available in the UK.
- 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.
- Line Type Intelligence Improve deliverability and minimize fraud by accurately identifying phone number type from mobile, landline, fixed VoIP, non-fixed VoIP, toll-free, etc.
- 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.
- 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.
- 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.
- 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.

Start for free

// Download the helper library from https://www.twilio.com/docs/node/install
const twilio = require("twilio"); // Or, for ESM: import twilio from "twilio";

// Find your Account SID and Auth Token at twilio.com/console
// and set the environment variables. See http://twil.io/secure
const accountSid = process.env.TWILIO_ACCOUNT_SID;
const authToken = process.env.TWILIO_AUTH_TOKEN;
const client = twilio(accountSid, authToken);

async function fetchPhoneNumber() {
  const phoneNumber = await client.lookups.v2
    .phoneNumbers("+14159929960")
    .fetch({ fields: "line_type_intelligence" });

  console.log(phoneNumber.lineTypeIntelligence);
}

fetchPhoneNumber();

# Download the helper library from https://www.twilio.com/docs/python/install
import os
from twilio.rest import Client

# Find your Account SID and Auth Token at twilio.com/console
# and set the environment variables. See http://twil.io/secure
account_sid = os.environ["TWILIO_ACCOUNT_SID"]
auth_token = os.environ["TWILIO_AUTH_TOKEN"]
client = Client(account_sid, auth_token)

phone_number = client.lookups.v2.phone_numbers("+14159929960").fetch(
    fields="line_type_intelligence"
)

print(phone_number.line_type_intelligence)

// Install the C# / .NET helper library from twilio.com/docs/csharp/install

using System;
using Twilio;
using Twilio.Rest.Lookups.V2;
using System.Threading.Tasks;

class Program {
    public static async Task Main(string[] args) {
        // Find your Account SID and Auth Token at twilio.com/console
        // and set the environment variables. See http://twil.io/secure
        string accountSid = Environment.GetEnvironmentVariable("TWILIO_ACCOUNT_SID");
        string authToken = Environment.GetEnvironmentVariable("TWILIO_AUTH_TOKEN");

        TwilioClient.Init(accountSid, authToken);

        var phoneNumber = await PhoneNumberResource.FetchAsync(
            pathPhoneNumber: "+14159929960", fields: "line_type_intelligence");

        Console.WriteLine(phoneNumber.LineTypeIntelligence);
    }
}

// Install the Java helper library from twilio.com/docs/java/install

import com.twilio.Twilio;
import com.twilio.rest.lookups.v2.PhoneNumber;

public class Example {
    // Find your Account SID and Auth Token at twilio.com/console
    // and set the environment variables. See http://twil.io/secure
    public static final String ACCOUNT_SID = System.getenv("TWILIO_ACCOUNT_SID");
    public static final String AUTH_TOKEN = System.getenv("TWILIO_AUTH_TOKEN");

    public static void main(String[] args) {
        Twilio.init(ACCOUNT_SID, AUTH_TOKEN);
        PhoneNumber phoneNumber = PhoneNumber.fetcher("+14159929960").setFields("line_type_intelligence").fetch();

        System.out.println(phoneNumber.getLineTypeIntelligence());
    }
}

<?php

// Update the path below to your autoload.php,
// see https://getcomposer.org/doc/01-basic-usage.md
require_once "/path/to/vendor/autoload.php";

use Twilio\Rest\Client;

// Find your Account SID and Auth Token at twilio.com/console
// and set the environment variables. See http://twil.io/secure
$sid = getenv("TWILIO_ACCOUNT_SID");
$token = getenv("TWILIO_AUTH_TOKEN");
$twilio = new Client($sid, $token);

$phone_number = $twilio->lookups->v2
    ->phoneNumbers("+14159929960")
    ->fetch(["fields" => "line_type_intelligence"]);

print $phone_number->lineTypeIntelligence;

# Download the helper library from https://www.twilio.com/docs/ruby/install
require 'rubygems'
require 'twilio-ruby'

# Find your Account SID and Auth Token at twilio.com/console
# and set the environment variables. See http://twil.io/secure
account_sid = ENV['TWILIO_ACCOUNT_SID']
auth_token = ENV['TWILIO_AUTH_TOKEN']
@client = Twilio::REST::Client.new(account_sid, auth_token)

phone_number = @client
               .lookups
               .v2
               .phone_numbers('+14159929960')
               .fetch(fields: 'line_type_intelligence')

puts phone_number.line_type_intelligence

curl -X GET "https://lookups.twilio.com/v2/PhoneNumbers/%2B14159929960?Fields=line_type_intelligence" \
-u $TWILIO_ACCOUNT_SID:$TWILIO_AUTH_TOKEN

Need help setting up phone number lookup?

Bring your ideal solution to life with technology partners and top-tier consulting partners like Deloitte Digital, Perficient, and more. View partners

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.

634M

total fraud blocks 1

$73.9B

saved by Verify Fraud Guard 1

5.1B+

user validations per year 2

90%

decrease in user validation time with Lookup Identity Match 3

Explore Verify

Lookup FAQs

Twilio Lookup is a phone number intelligence API. It helps you format, validate, and enrich phone numbers with carrier and risk data before you send a message, verify a user, or process a transaction. It is not a challenge-response authentication product.

Lookup helps you screen phone numbers before you trigger an OTP, create an account, or process a high-risk action. By checking risk and carrier signals up front, you can block suspicious traffic earlier, reduce unnecessary verification costs, and add less friction for legitimate users.

Basic formatting only validates phone number syntax, whereas Twilio Lookup checks live carrier network data for formatting, line status, and line type (VoIP, landline, mobile) in real time. Unlike point-solution lookup vendors, Twilio Lookup aggregates global carrier signals, SIM swap detection, reassigned number intelligence, and SMS pumping risk scores into a single API query.

Twilio Lookup supports line type intelligence, line status, identity match, SIM swap detection, call forwarding, reassigned number checks, caller name (CNAM), and SMS pumping risk scoring. Core use cases include blocking high-risk, non-fixed VoIP signups, stopping SMS toll fraud before sending OTPs, verifying user contact details against records, and cleansing contact lists to boost SMS deliverability rates.

Twilio Lookup uses a pay-per-query model starting with free basic phone number formatting and country code validation. Advanced risk signals, such as line type intelligence, SIM swap detection, and SMS pumping risk scoring, are billed as modular add-ons per API request. There are no upfront platform fees or monthly minimums on standard pay-as-you-go tiers, and high-volume enterprise accounts can access committed-use volume discounts.

A company should not use the Twilio Lookup API as a standalone challenge-response authentication mechanism. Lookup provides passive risk intelligence rather than active token delivery. Additionally, if your application only requires verifying phone possession via a passkey, TOTP, or SMS passcode without assessing phone number risk or carrier metadata, you should implement the Twilio Verify API directly instead of querying Lookup first.

No. Lookup is a phone number intelligence API. Verify is an authentication API. Use Lookup when you want to assess a number before taking action. Use Verify when you want to send and approve a verification challenge such as an OTP or another authentication step.

Twilio Lookup acts as a pre-screening to Twilio Verify. Applications query Lookup first to assess phone number risk, block high-risk VoIP or fraud-prone numbers, and identify line types. The application then routes low-risk users to cost-effective verification channels (like Silent Network Authentication or Push) and high-risk users to step-up verification via Verify, reducing overall authentication costs while blocking toll fraud.

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.

Start for free See Lookup API pricing

1 Total Verify Fraud Guard explicit savings and fraud blocks since Sept '23 up to 01 July ‘25

2 Twilio internal data for 2024

3 Tradier results with Twilio Lookup

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