A lot of very old SPA like heavy applications use XSLT. Basically, enterprise web applications (not websites) that predate fetch, rest, and targeted or still ta

A lot of very old SPA like heavy applications use XSLT. Basically, enterprise web applications (not websites) that predate fetch, rest, and targeted or still target Internet Explorer 5/6. There was a time where the standard way to build a highly interactive SPA was using SOAP services on the backend combined with iframes on the front end that executed XSLT in the background to update the DOM. Obviously such an approach is extremely out of date and you won't find it on any websites you use. But, a lot of critical enterprise software was built this way and is kind of stuck like this.