Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

PDF reader theme in FF 81

  • 4 replies
  • 2 have this problem
  • 70 views
  • Last reply by jscher2000

more options

With FF 81, I see the PDF reader has switched to a light theme, and I don't see a way to switch back to dark theme, the way it was before. How do I do it?

Thanks.

Chosen solution

Hi Jeenu, if you want all of Firefox's built-in pages to have a dark theme, as well as websites that check your system theme preference, you could try this, or maybe you already are using this based on advice from the above link:

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

(2) In the search box, type or paste ui.systemUsesDarkTheme

(3) Firefox should display a bar with some radio buttons to choose a new preference type, followed by a + button. Choose Number and click the + button:

(4) Edit the value to 1 and then click the blue check mark button or press Enter/Return to save the change.

For reference, this value is used to answer web pages' inquiries about your preferred color scheme. Setting it manually overrides Firefox answering the inquiry based on your system theme:

  • 0 => Light
  • 1 => Dark
  • 2 => No Preference

Success?

Read this answer in context 👍 1

All Replies (4)

more options

I believe this is currently a bug that the developers are looking to address (see issue #12290).

Helpful?

more options

Chosen Solution

Hi Jeenu, if you want all of Firefox's built-in pages to have a dark theme, as well as websites that check your system theme preference, you could try this, or maybe you already are using this based on advice from the above link:

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

(2) In the search box, type or paste ui.systemUsesDarkTheme

(3) Firefox should display a bar with some radio buttons to choose a new preference type, followed by a + button. Choose Number and click the + button:

(4) Edit the value to 1 and then click the blue check mark button or press Enter/Return to save the change.

For reference, this value is used to answer web pages' inquiries about your preferred color scheme. Setting it manually overrides Firefox answering the inquiry based on your system theme:

  • 0 => Light
  • 1 => Dark
  • 2 => No Preference

Success?

Helpful?

more options

Is there a way to change the PDF reader to dark theme without altering the rest of the UI's theme? Also see my question on the topic or another relevant one.

Modified by Václav Trpišovský

Helpful?

more options

Hi Václav, my answer in https://support.mozilla.org/questions/1305573 is the only way I know to modify the PDF viewer without affecting other built-in pages.

Helpful?

Ask a question

You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.