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New member
Status: Trending idea

Hello everyone...

I use Firefox a lot of years and i am very happy with the interface.

But i saw that there is no built-in option to change  the Mode of Embedded PDF Viewer in to Dark

Is possible to be implemented in the near Future...?

Thanks in advanced.

Status changed to: New idea
Community Manager
Community Manager

Thanks for submitting an idea to the Mozilla Connect community! Your idea is now open to votes (aka kudos) and comments.


Hi, there is a hidden setting to change the background and toolbar areas to a dark mode, but the document will still follow the author's colors, so that's probably not what you're looking for.

But just in case you want to try it, here's how:

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. Please keep in mind that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(B) In the search box in the page, type or paste pdfjs.viewerCssTheme and pause while the list is filtered

(C) Double-click the preference to display an editing field, and change the value to one from the below list, then press Enter or click the blue check mark button to save the change.

  • 0 => auto-detect
  • 1 => Light background
  • 2 => Dark background



New member


Status changed to: Trending idea
Community Manager
Community Manager

Hey all,

Here with an exciting update…

Your idea has quickly received a great deal of votes (kudos) and support here in the Mozilla Connect community, so we are upgrading the status to “Trending idea.” This means it’s now one step closer to reaching our internal teams for review—learn more about The Idea Journey.

Please keep the conversation going (the more details, the better) and stay tuned for updates 😃

-The Community Team

New member

Some programs for pdf have an option to change white background and black texts to

black background and white text.

I miss this option in firefox, so I have to use program as pdf viewer in linux

Strollin' around

PDF Reader Dark Mode Options

Would be great for the PDF reader to have a setting, similar to reader view, for dark, light, or automatic background and toolbar colour

Edit: I was testing on a new profile and I noticed that dark mode does in-fact exist for the PDF reader and that privacy.resistFingerprinting is what's causing the 'issue'. As such, an interface allowing the user to toggle dark/light mode such as the one is reader view would be great!

Community Manager
Community Manager

(Note: a similar idea has been merged into this thread)

New member

I've been searching for a work around and I'm pretty disappointed. I'm studying all the time and this white theme will be the reason I'll go blind. 😞


It is possible to select colors for all web pages from the preferences:

If you want to do it for PDFs only, you can tweak the following prefs from about:config:

- pdfjs.forcePageColors
- pdfjs.pageColorsBackground
- pdfjs.pageColorsForeground