Facebook Pixel specifically for Shopify.
https://help.shopify.com/en/manual/promoting-marketing/analyze-marketing/facebook-pixel
Analytics and Tracking
Get access to data on 1,340,884 websites that are Facebook Pixel for Shopify Customers. We know of 528,121 live websites using Facebook Pixel for Shopify and an additional 812,763 sites that used Facebook Pixel for Shopify historically and 354,567 websites in the United States.
Facebook Pixel for Shopify websites that are also using other technologies.
Get a list of 1,340,884 websites using Facebook Pixel for Shopify which includes location information, hosting data, contact details, 528,121 currently live websites and an additional 285,363 domains that redirect to sites in this list. 812,763 sites that used this technology previously and 354,567 websites in the United States currently using Facebook Pixel for Shopify.