• Calls labelled unknown source are calls that Nimbata could not attribute to a tracked marketing source or session.
• This classification describes the result of attribution, not the cause.
• Several different scenarios can produce it.
• The most common cause is a caller dialing the tracking number directly.

E.g. Entering it manually, calling from a printed list or brochure, or using the number outside of a tracked environment.

Unknown source can also occur whenever attribution data is simply unavailable at the time the call is placed.

What to check

Verify how the tracking number is being displayed

• Make sure your tracking numbers are only shown dynamically via your website or in tagged materials where source data can be captured.
• If the number appears anywhere else, on printed materials, saved in a contact list, or shared outside tracked pages, callers may dial it directly and no source information will be sent.

Review your dynamic number insertion setup

• If you expect calls to be attributed to tracked channels (UTM tags, campaign links, ad sources), confirm that the DNI script is installed correctly on every page you want to track.
• An incorrect or incomplete DNI setup results in calls landing without source attribution.
• Calls with an unknown source do not necessarily indicate a problem with your tracking numbers.
• They reflect calls that could not be mapped to a known marketing source based on how the call originated.
• If you're seeing a higher-than-expected number of unknown source calls, reviewing how and where your tracking numbers are displayed is the right first step.

Detailed guide: DNI script 101: how to install and configure it

Detailed guide: Why are numbers not swapping on my website?

Troubleshooting: Setup looks correct but no calls yet: what to check

Updated on: 02/04/2026