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Firefox devtools: can't turn responsive design mode on

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  • 4 이 문제를 만남
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  • 최종 답변자: cor-el

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Suddenly Firefox doesn't react neither on pressing Ctrl+Shift+M, nor on pressing "responsive design mode" button on the toolbar. The button looks like the mode is already on (but it's not) and it doesn't react on mouse clicks. Tools -> Web Developer -> Responsive Design Mode is also of no good.

What's wrong and how can I fix it?

(Firefox is up to date. The problem wasn't the case right after the last update and appeared suddenly.)

Suddenly Firefox doesn't react neither on pressing Ctrl+Shift+M, nor on pressing "responsive design mode" button on the toolbar. The button looks like the mode is already on (but it's not) and it doesn't react on mouse clicks. Tools -> Web Developer -> Responsive Design Mode is also of no good. What's wrong and how can I fix it? (Firefox is up to date. The problem wasn't the case right after the last update and appeared suddenly.)

모든 댓글 (10)

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Do you see any error messages in the Browser Console?

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No, I don't. I checked all items in all submenus I could (I mean "Net", "CSS", "JS" and so on), but I only see some error messages from site's CSS and a lot of other info, but nothing of it seems related to developer tools itself. When I click on "responsive design mode", nothing bumps up in the browser's console.

(I'm certain that I'm viewing namely browser's console. I opened it using Ctrl+Shift+J)

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Does it make a difference whether multi-process is enabled or disabled?

See the "Help -> Troubleshooting Information" page under Application Basics: Multiprocess Windows for details.


You can disable multi-process windows in Firefox by setting these prefs to false on the about:config page.

  • browser.tabs.remote.autostart = false
  • browser.tabs.remote.autostart.2 = false

You can open the about:config page: via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

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It says "Multiprocess Windows 0/1 (Disabled by add-ons)" and it doesn't change when I toggle both browser.tabs.remote.autostart settings. Doesn't affect the initial issue as well.

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I reinstalled the Firefox, the problem remains.

Maybe it's somewhere in the profile folder. Where do devtools store their cache, state or something?

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I've noticed that when I press Ctrl+Shift+M the scrolling bar becomes "mobile" (thinner, trasparent, round borders). Nothing else changes, though. And I can't revert it pressing Ctrl+Shift+M again. Even page reload doesn't work.

UPDATE: I created new blank profile and there devtools work properly. The question is now how do I make them work on my existing profile.

글쓴이 1234ru 수정일시

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I found some kind of solution.

Examining devtools* setting in about:config I've noticed that settings' names in new profile differ from the ones in the old one. In particular, there is no settings named devtools.responsiveUI.*, except of one. I deleted all those settings in old profile and now it works!

Basically, the problem is responsiveUI version in old profile and in a new one somewhy differs significantly, and Firefox's update didn't help with it (although it should, as devtools are core part of Firefox itself (as far as I know) and should be updated for all profiles). For example, in old profile I still don't have network throttling tools etc.

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Note that there are two different RDM versions. The 'classic' version (black background) that is used when multi-process is disabled and a new version that is used when multi-process is enabled and that is centered and has a white background and has the device selector. I don't know what prefs are used by both versions, but there could have been a conflict.

I normally only see scroll bars when I drag the mouse in the location where the scroll bar should be.

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That makes sence. I want to test it. How do I enable/disable multi-process?

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You can check "Multiprocess Windows" to see the current state.

  • "Help -> Troubleshooting Information" -> Application Basics: Multiprocess Windows

When multi-process is enabled and the first number is not zero (1/1) then you get the new design. You can disable multi-process by toggling the opt-in pref to false on the about:config page with a double-click to see the old design.

  • browser.tabs.remote.autostart.2 = false

You need to close and restart Firefox to make the change effective.