> ## Documentation Index
> Fetch the complete documentation index at: https://plivo.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Number Masking Overview

> Hide phone numbers between parties while enabling seamless communication

Phone number masking hides the phone numbers of parties in a call from each other. Many businesses find it advantageous to anonymize communication between two parties.

## Use Cases

* **Food/grocery and ecommerce delivery apps** connect a delivery agent to a customer without revealing personal numbers.
* **Ride-hailing apps** connect a driver to a passenger while keeping both numbers private.
* **Classified ad listing apps** connect sellers to buyers, or service providers to customers anonymously.
* **Healthcare platforms** connect patients with providers while maintaining privacy compliance.

## How It Works

Plivo's Number Masking API handles both virtual number assignment and call flow management:

1. Your application sends the real phone numbers of both parties via an API request
2. Plivo creates a session and assigns a virtual number from your account
3. You display the virtual number to both participants
4. When either party calls the virtual number, they're automatically connected to the other party
5. The caller ID shows the virtual number, keeping real numbers hidden

## Key Concepts

### Session

A session represents a unique pairing between two parties. Within a session:

* Parties can make multiple (non-concurrent) masked calls
* A virtual number is assigned for the session duration
* You control session expiry and call time limits
* Call recordings and callbacks can be configured

### Interaction

Every conversation between parties in a session is an interaction. Each interaction:

* Has a maximum of two communication legs
* Tracks call details for both parties
* Contains resources for monitoring and billing

### Virtual Numbers

Plivo optimizes virtual number allocation to minimize the numbers needed:

* A single virtual number can host thousands of sessions
* Quality is not impacted as numbers are just identifiers
* Call media flows through dedicated channels for each interaction

## Calling Scenarios

### Click-to-Call

One party initiates a call by clicking a button in your app:

1. Party A sees the virtual number and dials it
2. Plivo connects the call to Party B
3. Both parties see only the virtual number

### Request-a-Call

Your app initiates a call to both parties:

1. User clicks "Call Me" and provides their number
2. Plivo calls the first party
3. When answered, Plivo calls the second party and bridges them

This is useful when:

* Customers are roaming and can't call out
* You want to control outbound calling costs

## Next Steps

* [Virtual Number Allocation](/number-masking/concepts/virtual-number-allocation) - Calculate how many numbers you need
* [PIN-based Authentication](/number-masking/concepts/pin-based-authentication) - Authenticate callers from unknown numbers
* [Session API Reference](/number-masking/api/session) - Create and manage masking sessions