Intercom is an American software company that produces a messaging platform which allows businesses to communicate with prospective and existing customers within their app, on their website, through social media, or via email.
Zendesk is a cloud-based help desk management solution offering customizable tools to build customer service portal, knowledge base and online communities.
54 sites run both Intercom and Zendesk. That is 10% of the sites using Intercom, 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.