means the server delivers just a shell, often only an empty container such as <div id="app"></div> plus a script. The visible page only appears once the browser loads and executes the JavaScript and fetches data from application programming interfaces ().

For users this can work perfectly. For and , however, pure CSR is risky because crawlers initially receive only the near-empty shell.

CSR is especially problematic when these elements are created client-side only:

  • heading () and main text,
  • and navigation,
  • title, and canonical,
  • ,
  • product data, prices or availability.

More robust alternatives are server-side , static site generation or clean prerendering.