I'm trying to figure out the simplest possible way to export an html document from org-mode and have it include a working custom-element.

I've tried the following, but it gives me an error message in the console

<script type="module" src="https://raw.githubusercontent.com/PolymerElements/paper-button/master/paper-button.js"></script>
<paper-button raised class="indigo">raised</paper-button>

browser error message:

Loading module from “https://raw.githubusercontent.com/PolymerElements/paper-button/master/paper-button.js” was blocked because of a disallowed MIME type (“text/plain”).

I took the component from:


  • I presume your browser is Firefox? This does not happen in Chrome (yet?) and in any case has nothing to do with emacs or Org mode. The Learn More link in the console supposedly explains more, but not to me.
    – NickD
    Aug 14, 2020 at 2:50

1 Answer 1


It's a CORS issue, not a problem related to Emacs, org-mode or anything in the editing side.

Modules should be of MIME-type text/javascript or they won't load in any browser implementing the specification.In this case this translates to the fact that you're including a file from raw.githubusercontent.com which will serve text/plain MIME, thus it won't be accepted by browsers.

One possible workaround for this is using an alternative url which will honor the MIME-type as could be jsdelivr.net - There may be others, but I just know this one.

So, using this url as src: https://cdn.jsdelivr.net/gh/PolymerElements/paper-button/paper-button.js

will deliver the file without CORS errors.

This will fix your current issue, but probably there it will be more to do to make the thing work as you pretend.

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