To enable the highest accuracy tracking of Pinterest Ads follow this guide on how to place the ThoughtMetric tracking parameter on your Pinterest Ads.
ThoughtMetric Pinterest tracking parameter:
tmsrc=pinterestad&tmcid={campaignid}&tmsid={adgroupid}&tmid={adid}
To use our tracking parameters on Pinterest, you will need to update the URL in the “Destination link” section of the ad settings.
How to handle parameters that are already in the tracking template
If you already have some tracking parameters in the destination link field, don't worry, you can use the ThoughtMetric tracking parameters in addition to any tracking you already have in place.
To use the ThoughtMetric parameters alongside your existing tracking template you will want to append our tracking parameters to the end of your existing UTM string by using a "&" symbol starting with the tmsrc parameter.
For example If you already had the following text in your tracking template:
https://mystore.com?utm_source=pinterest
You would want to append the ThoughtMetric tracking parameters so that the end result looks like this:
https://mystore.com?utm_source=pinterest&tmsrc=pinterestad&tmcid={campaignid}&tmsid={adgroupid}&tmid={adid}