Definition · Call Tracking
Dynamic number insertion (DNI)
Also known as: DNI, dynamic number insertion, number pool
Dynamic number insertion (DNI) is a call-tracking technique that swaps the phone number shown on a website per visitor, so each session displays a unique tracking number. When that number is called, the platform attributes the call to the exact ad, keyword, or source that brought the visitor in.
DNI is the mechanism that makes phone calls measurable the way web clicks are. A small script on the website replaces the displayed phone number with one drawn from a pool, keyed to how the visitor arrived — which campaign, keyword, or referrer. Because each visitor sees a number tied to their source, an inbound call can be matched back to the marketing that produced it.
The cost lever buyers miss is the number pool. Session-level DNI needs enough simultaneous tracking numbers to cover concurrent visitors without two people seeing the same number; more traffic means a bigger pool, and tracking numbers are usually billed per number per month on top of the base plan. A plan that looks cheap can become expensive once the pool is sized for real traffic.
When comparing call-tracking vendors, the DNI questions are: how many tracking numbers and how many included minutes come with the tier, the per-number and per-minute overage rates, and whether visitor-level (not just source-level) attribution is supported.