title: Restrict static file access to logged in users
body: <p>I want to restrict files to be available to logged in users, but otherwise return a 403 error or similar.  For example a user should be able to view/download <code>/static/data/example.csv</code> only if they're logged in.</p>
  
  <p>I know how to control the actual displaying of the files using Flask-Login if they're not logged in, but not how to block access to the file if they visit the link directly in their browser.</p>