What is the difference between encodeRedirectUrl and encodeURL?

encodeURL and encodeRedirectURL are methods of the HttpResponse object. Both rewrite a raw URL to include session data if necessary. (If cookies are on, both are no-ops.)

encodeURL is for normal links inside your HTML pages.

encodeRedirectURL is for a link you're passing to response.sendRedirect(). It has slightly different syntax requirements too gory to get into here.

See this FAQ for more details.