PWA is the more common of the two in our index: it runs on 13,339 websites against 68 for X-Clacks-Overhead, and 12 sites use both. Counts come from real scans, not vendor claims.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.
X-Clacks-Overhead is a non-standard HTTP header used to transmit tribute messages within server responses.
12 sites run both PWA and X-Clacks-Overhead. That is 18% of the sites using X-Clacks-Overhead, 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.