# DID
> Direct Inward Dialing – assigns individual phone numbers to each user without requiring separate lines

DID (Direct Inward Dialing) gives each user a unique phone number routed over shared VoIP trunks.

## What is DID?
Direct Inward Dialing (DID) is a telephony feature that assigns individual phone numbers to users or extensions within a [PBX](/voip-glossary/pbx/) system, without requiring a separate physical line for each number. Callers dial the DID number directly, bypassing the receptionist or auto-attendant.

## DID in VoIP
In VoIP environments, DIDs are virtual numbers delivered over [SIP trunks](/voip-glossary/what-is-sip-trunking/). This makes it easy to provision local, toll-free, or international numbers for any user, regardless of their physical location.

## Benefits for service providers
DID numbers enable CSPs to offer competitive numbering plans to business customers. Combined with [number porting](/voip-glossary/number-porting/), subscribers can keep existing numbers when switching to a VoIP-based softphone solution.

## Related Terms
- [What is SIP trunking?](/voip-glossary/what-is-sip-trunking/)
- [Number Porting](/voip-glossary/number-porting/)