What is "automatic" about the "Automatic Zoom" in Firefox's built-in PDF viewer? What is Firefox "automatically" doing? I have to ask this question because View PDF files in Firefox does not explain what "Automatic Zoom" does.

Is it just adjusting the zoom level to fit the current dimensions of the Firefox browser window?

I'm currently running Firefox Version 67.0.4 on Ubuntu 19.04.


Restores your PDF to the default view, which is generally full page view. So, yes, it just fits your PDF within your browser window.

Firefox Keyboard and Mouse Shortcuts confirms this.

Full page zoom is set by default.

Can I change default display width in built-in PDF Viewer? tells you how to change the PDF default zoom value.

You can set a default view like this: enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named pdfjs.defaultZoomValue. double-click it and change its value to page-width (this should have an effect on all new documents you open).

  • Not sure who gave this guy a downvote (I wish folks wouldn't do that without adding a comment for why the downvote). However, Poyda, please update your answer with a link to somewhere in the official documentation that states that it fits the PDF to the browser window. – bgoodr Jul 12 at 14:48
  • 1
    @bgoodr - Answers which only provide a link to a reference, without quoting and citing that reference, is a very reasonable reason to downvote an answer. However, since it's an answer to your question, If you find the answer helpful then you should upvote it. I went and made the changes that would make this a quality answer. I won't be doing it again for the author though. – Ramhound Jul 14 at 22:58

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