What is a DID number?
A DID (Direct Inward Dialing) number is a phone number that rings directly at a specific extension, user or team inside a company's phone system, without going through a main line or receptionist. It lets one system hold many direct numbers.
How it works
A carrier assigns a block of numbers to a company's phone system, often over a SIP trunk. When someone dials one of them, the carrier passes the dialed number to the PBX.
The PBX reads that number and rings the extension, user or group it is mapped to, so the caller reaches the right person directly.
In a cloud phone system the same idea applies without any trunk: each number you add is a DID you can assign to a person, a team or a menu.
Why it matters
01Direct access
Clients reach their account manager without going through reception.
02Fewer lines
Many DIDs share a smaller number of channels, since not everyone calls at once.
03Tracking
A separate number per campaign, team or region shows where calls come from.
Allo and DID number
In Allo, every number you add works like a DID: assign it to one person, a team, an IVR or the AI receptionist, in 50+ countries.
Related terms
The terms that usually come up in the same conversation.
All glossary terms
SIP trunking
Virtual lines that connect a PBX to the phone network over the internet.
Read the definition
Frequently asked questions
Often in practice. DID describes how the number reaches a specific destination inside a phone system; virtual describes that it is not tied to a physical line. Most DIDs today are virtual numbers.
An extension is an internal short number, only reachable inside the system or through the main line. A DID is a full public number that outside callers can dial directly.
Many can, depending on the provider and the country. In the US, texting from a local DID requires A2P 10DLC registration.