NUMBER MASKING 

Protect privacy with number masking

Number masking hides real phone numbers by using temporary proxy numbers, allowing customers, partners, and workers to communicate securely. Built into our programmable Voice API, this privacy feature supports global, compliant, and scalable voice and SMS communications.

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Join over 150,000 businesses, including 8 of the 10 largest tech companies in the world

SAFETY, TRUST, AND REACH

Why businesses choose Voice API number masking

Number masking keeps conversations private by hiding real phone numbers and using local proxy numbers. The API-first design gives you full control, global reach, and built-in privacy compliance. 

Privacy protection

Temporary proxy numbers hide real phone numbers, keeping caller information private and safeguarding every interaction. 

On-platform control 

Keep conversations on your platform. By managing the communication channel, you prevent users from taking transactions offline and bypassing your service. 

Trusted global reach

Local numbers in over 70 countries and 16,000 cities increase answer rates and build trust with customers worldwide.
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PRIVACY & SECURITY

Protect user privacy and build brand trust by masking phone numbers

Number masking replaces real phone numbers with temporary proxy numbers, keeping identities private. TLS/SRTP encryption and compliance with ISO 27001, GDPR, and STIR/SHAKEN keep every call secure across voice and SMS. 

  • Anonymizes phone numbers end-to-end 

  • TLS/SRTP-encrypted connections 

  • ISO 27001 and GDPR compliant

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ON-PLATFORM ENGAGEMENT

Boost answer rates with local numbers worldwide 

Reach customers with proxy numbers from over 70 countries and 16,000 cities. Show familiar, local caller IDs to increase trust, boost pickup rates, and tailor experiences to each market.

  • Local numbers improve reach

  • Consistent caller trust signals 

  • Programmable for each region

WAYS TO USE NUMBER MASKING 

Where number masking makes a difference 

Ride-sharing & delivery

Secure calls between drivers and passengers without sharing personal numbers, protecting everyone during and after every trip.

Marketplaces

Connect buyers and sellers for negotiations while keeping their phone numbers private and on-platform.

Healthcare

Support private doctor-patient conversations and sensitive follow-ups with masked numbers and enterprise-grade security. 

Customer support 

Let agents call customers from masked numbers so personal lines stay personal and brand trust remains high. 

MASKING MADE EASY 

What you get with Sinch Voice API number masking

Two-way masking 

Bidirectional privacy for both voice and SMS so neither party’s real number is exposed.


Temporary, controlled connections 

Connect two users only for the duration you define—like during a delivery or a support case.

Global proxy numbers 

Access local numbers in over 70 countries and 16,000 cities to improve reach and answer rates.


Programmable via REST APIs 

API-first design with quick-start guides lets you control and monitor masking flows in minutes.

Recording & transcription (BYOS) 

Bring your own storage for full data ownership and compliance. We never keep your recordings. 

Callback & event logs 

Real-time callbacks and clear logs make debugging, analytics, and reporting seamless. 


TLS/SRTP & compliance 

ISO 27001, GDPR, and STIR/SHAKEN compliance plus TLS/SRTP encryption safeguard every call. 


SDKs for all platforms 

Native SDKs for iOS, Android, Web, Java, Python, Node.js, and .NET speed up integration for any stack. 


Frequently asked questions about number masking

Number masking works by substituting a person’s real phone number with a temporary, virtual one provided by the Sinch Voice API. When a call or SMS is sent, it’s routed through this proxy number, ensuring that neither party can see the other’s private contact details. 

Phone number masking technology masks real phone numbers during calls or SMS by substituting a temporary virtual number, creating private and secure communication. 

Yes, Sinch Voice API supports two-way number masking for both voice and SMS, with full control via REST APIs and webhooks. 

Sinch Voice API is ISO 27001 and GDPR compliant, and STIR/SHAKEN compliant in the US and Canada. BYOS is required for recording. 

Proxy numbers are available in over 70 countries and 16,000 cities, providing local presence to improve reach and answer rates. 

You can integrate number masking into your application using the Sinch Voice API. The integration is managed programmatically using REST APIs to control call flows and webhooks (callbacks) to receive real-time events. To accelerate development, Sinch offers SDKs for all major platforms, including iOS, Android, Web, Java, Python, and .NET. 

Talk to an expert about number masking

Learn how to protect user privacy, keep conversations on-platform, and scale secure voice and SMS worldwide.