The problem: you want the path / to serve public/index.html and /foo/, to serve to public/foo/index.html.

This is a fork of elitheeli/sinatra-index.

I adjusted it to add a trailing slash with a 301 redirect.

require 'sinatra'
require 'sinatra-index'

configure do
  register Sinatra::Index
  use_static_index 'index.html'
end

# ... Sinatra routes ...