title: JupyterLab 3.0.16: Exporting HTML results on "Blocking request with no referer" and "403 Blocking request from unknown origin"
body: <p>I am having what seems to be a perennial problem with JupyterLab users but when applying the solutions that have worked with others, I am not getting positive results.</p>
  <p>This problem is new, only emerging over the past few weeks.</p>
  <p>This problem is occurring only with JupyterLab (not Jupyter Notebook) for ...</p>
  <ul>
  <li>Operating System: macOS-11.4-x86_64-i386-64bit</li>
  <li>Miniconda Build: 4.10.1</li>
  <li>Python Version: 3.8.10</li>
  <li>Browsers:
  <ul>
  <li>Safari for MacOS 14.1.1 (16611.2.7.1.4)</li>
  <li>Chrome for MacOS 91.0.4472.77 (Official Build) (x86_64)</li>
  </ul>
  </li>
  <li>Jupyter Suite Versions:
  <ul>
  <li>jupyter                       1.0.0</li>
  <li>jupyter-client                6.1.12</li>
  <li>jupyter-console               6.4.0</li>
  <li>jupyter-core                  4.7.1</li>
  <li>jupyter-server                1.8.0</li>
  <li>jupyterlab                    3.0.16</li>
  <li>jupyterlab-pygments           0.1.2</li>
  <li>jupyterlab-server             2.5.2</li>
  <li>jupyterlab-widgets            1.0.0</li>
  </ul>
  </li>
  </ul>
  <p>Problem:</p>
  <p>When working with a <em>locally</em>-run JupyterLab (i.e., using a URL of 128.0.0.1:8888, or localhost:8888), when Exporting a IPYNB notebook to HTML, txt or other format, I get the following two errors:</p>
  <pre><code>[W 2021-05-27 14:50:15.795 ServerApp] Blocking request with no referer
  [W 2021-05-27 14:50:15.795 ServerApp] 403 GET /nbconvert/html/Untitled.ipynb?download=true (::1): Blocking request from unknown origin
  </code></pre>
  <p>However, when using the same IPYNB notebook (even one simply consisting of a single cell saying <em>print(&quot;hello&quot;)</em>, in a basic Jupyter <em>Notebook</em> session the exports function satisfactorily and create nice viewable HTML and PDF files.</p>
  <p>I have search across solution resources and the closet thing I've seen for guidance has been to add the change two lines in the jupyter configuration files as so:</p>
  <pre><code>c.NotebookApp.allow_origin=''
  c.NotebookApp.allow_remote_access = True
  </code></pre>
  <p>I have tried this on more than one fresh install of Minconda and this does not yield favorable results.  (Some of these recommendations are coming for users of JupyterHub, not JupyterLab).</p>
  <p>I have a &quot;gist&quot; from a sample JupyterLab session available showing both</p>
  <ul>
  <li>the debug log of the specific problem if a notebook with the single cell containing &quot;print('Hello')&quot;</li>
  <li>the output of the jupyter troubleshoot command showing the configuration of my miniconda/python/jupyter setup.</li>
  </ul>
  <p><a href="https://gist.github.com/wjcapehart/a6145ae8e7e1f967bab7412fd118c455" rel="noreferrer">https://gist.github.com/wjcapehart/a6145ae8e7e1f967bab7412fd118c455</a>
  (my username is replaced with ${HOME} in the Gist files.)</p>
  <p>Does anyone have any ideas here?</p>
  <p>Cheers and Thanks
  Bill</p>