sorry if this is basic question but couldn't find answer in docs.....basicaly in a SPA setup I want any requests that would normally return a 404 to redirect to say main index.html....is there way to configure this in Ktor?

I think you can do that with the StatusPage feature

Thanks @Julien Salvi @christophsturm, will take a look at those. I'd like ideally to see firstly if this can be done without pulling in 3rd party library

I agree, but you can look there to see how its done

Using StatusPage you can redirect to index at every 404 https://ktor.io/docs/status-pages.html#status