A KPI in SEO or Key Performance Indicator in SEO is used to measure the value that an SEO campaign offers its client and ascertain the success of the performance of the said campaign over time within certain parameters set before the campaign began. Tracking KPIs like number or leads, rankings, the best ranking keyword pages, the events being triggered through Google Tag Manager tags, and heatmapping the user behavior throughout the process is essential to improving the ROI of the campaign.