What is dynamic number insertion (DNI)?

Dynamic number insertion is the technique that makes call tracking work on your website: a small script swaps the phone number a visitor sees based on how they arrived, so a caller from a Google ad sees a different tracking number than one from Facebook or organic search.

When the call comes in, it forwards to your real business line as normal — but now the call record carries its source, the campaign, and often the exact pages the visitor viewed first.

Done correctly it's invisible to customers and safe for SEO (your primary number stays consistent in structured data and listings while the visible number swaps per session).