Cloudflare Browser Insights is the more common of the two in our index: it runs on 12,378 websites against 826 for Quantcast Measure, and 120 sites use both. Counts come from real scans of each site's home page, not vendor claims, and cover the sites in TechLookup's index rather than the whole web.
Cloudflare Browser Insights is a tool that measures the performance of websites from the perspective of users.
Quantcast Measure is an audience insights and analytics tool.
Within the analytics sites we have indexed, Cloudflare Browser Insights holds 15% and Quantcast Measure 1.0%.
120 sites run both Cloudflare Browser Insights and Quantcast Measure. That is 15% of the sites using Quantcast Measure, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.