Dial prefix

A dial prefix is a small piece of text VICIdial sticks onto the front of every phone number before it places the call. The person you are calling never hears it and it never appears on their caller ID. Its only job is to match a rule in your Dialplan so the call leaves your server through the route you intended. Think of it as a routing label that gets peeled off before the digits ever hit the network.

Each Campaign has its own dial prefix field. When an agent or the dialer fires a call, VICIdial builds the dialstring as the prefix plus the number. The dialplan then matches that prefix, strips it, and sends the remaining digits out the chosen Trunk. Because the prefix decides the route, you can point one campaign at one Carrier and another campaign at a completely different one just by changing this single value, with no edits to the leads themselves.

How it is used in practice

Operators lean on dial prefixes for a handful of everyday tasks:

• Splitting traffic across carriers for cost or quality, which pairs naturally with Least-cost routing in the dialplan.
• Sending test calls down a dedicated route while real production traffic stays untouched on its own path.
• Failing a campaign over to a backup carrier by swapping one prefix when the primary route has trouble.

Do not confuse the dial prefix with a Phone Number Prefix, which is about the digits of the number itself rather than the route it travels. The dial prefix lives in the dialplan layer and is invisible to the called party. If your campaign suddenly fails with no audio, a fast busy, or a hangup before it even rings, a mismatched or missing prefix is one of the first things worth checking, because the dialplan has no rule to catch the string you are sending.