Questions tagged [firefox-developer-tools]

The Firefox Developer Tools are the built-in development tools in Mozilla Firefox.

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How to always open in Responsive Design Mode?

How to make Mozila Firefox always open Youtube site in Responsive Design Mode? So that i don't have to always press Ctrl+Shift+M.
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1 answer
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no grid layout in firefox dev tools when in shadow root

When I have a CSS grid inside a shadow root, Firefox dev tools doesn't show it in the layout grid pane. It just says CSS Grid is not in use on this page CSS Grids that are not inside a shadow root do ...
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Is it possible to copy CSS line number in Firefox?

It is really annoying to remember and type in line numbers of CSS rules, maybe there is some way to navigate quickly to the right line directly in my IDE? I can't believe nobody has an issue like this....
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How to edit a config in about:config via command line WITHOUT having to restart Firefox to have it applied?

I'm trying to automate a process and want to edit a config in about:config via command line WITHOUT having to restart Firefox to have it applied. How can I do that? I'm under Linux. I tried editing ...
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Is it possible to search the developer toolbox on Firefox?

I can't find a way to search inside the developer toolbox (menu that appears when pressing CtrlAltShiftI). Or is it not possible to search there at all? I'm on Firefox v79 if that helps.
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Search / Find / Replace in Firefox Developer Tools Debugger

I've looked all over but I can't find anything (not even in the MDN Firefox Developer Tools Help Pages) which explains how, when I'm looking at the Debugger in Firefox Developer Tools I can request to ...
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3k views

How to download a website's source maps?

I don't want to write a complete script for this; there must be some simple way to download source maps. By this I mean go to a website (assuming it has source maps) in Firefox, open Developer Tools, ...
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Debug MSE and HTML5 videos in Firefox

In Chrome and Opera there is media-internals for getting detailed information on what's going on when a site is about to play a html5 video. How can I debug video sites in Firefox? (Beside of ...
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Meaning of the notification Firefox seems slow to start?

Hi Firefox experts, When launching Firefox, it sometimes displays at the bottom a notification saying "Mozilla Firefox seems slow... to... start." Is this an official notification type within ...
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1 answer
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how to use ctrl + 1 to switch to previous tab in firefox?

I'm using firefox 71 in mac os, i'd like to use ctrl+1 to switch to previous tab rather than command+shift+tab, how to achieve this? i tried an add-on called custom key but not working, i also tried ...
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2 votes
1 answer
40 views

How to find out which Firefox extension prints to console

One of the Firefox extensions I installed prints 'undefined' to the console. It happens in a file cs.js. Is there any way to find out which extension does that, apart from disabling them one by one?
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537 views

Intercepting input entered into the Firefox developer console?

I am currently in the process of moving my web-dev work from classic IDEs to the web browser console. The console is basically a JavaScript REPL, which is great, but that also means it can only ...
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433 views

Setting the text input value of the Firefox developer console?

I am currently in the process of moving my web-dev work from classic IDEs to the web browser console. This involves frequent editing of existing source code, which right now means... logging the ...
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  • 125
3 votes
1 answer
1k views

How to turn off accessibility in Firefox?

I was turned on accessibility service on developer tool but I cannot turn if off. The turn off button said Accessibility service cannot be turned off. It is used outside Developer Tools. From ...
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1 vote
1 answer
20 views

Searching for CSS rule in all an element's children, not just selected elements

In the Firefox inspector's Inspector tab the CSS rules pane has a search tool but it only searches the element currently selected in the HTML pane. For example, I know there is a rogue width ...
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469 views

How to prevent the Firefox developer tools window from focusing on page reload?

I've been annoyed by Firefox developer tools window always restoring from minimized state (focusing) every time the page I'm working on is reloaded. I'm not sure if this is a quirk or a feature but ...
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3 votes
1 answer
884 views

Cannot remove breakpoints in Firefox debugger

I added some breakpoints in Firefox debugger and when I removed them, they just disappear in the Breakpoints list.Then, when I load the page, it still pauses at the breakpoints. If I close the ...
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8 votes
1 answer
5k views

How do I modify a variable at a breakpoint in Firefox Developer Edition?

I would like to be able to edit a variable after setting (and hitting) a breakpoint, in either Firefox or Firefox Developer Edition. It seems that it used to have this feature, but it was removed ...
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1 answer
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Can I use Firefox Dev tools in a seperate button on the task bar?

I'm on Windows 10 and am using Firefox Developer Edition. In Chrome, if I open the Dev Tools, I can undock the Dev Tools into a separate window. This creates a new task bar button specifically for the ...
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19 votes
2 answers
7k views

How to view log of network requests across tabs in Firefox?

Within Firefox, I would like to see all network requests being made by Firefox. Using Firefox developer tools works great for this. Just open the developer tools, click on Network, and there you go. ...
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3 votes
1 answer
7k views

How do I search with XPath in Firefox Quantum 65?

I used to use FirePath and FireBug for XPath support in Firefox a long time ago, but those tools haven't worked with Firefox for some time. I was disappointed but found that I could still use the find ...
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2 votes
2 answers
904 views

How can I turn on accessibility features in Firefox?

Firefox's developer tools has an Accessibility section that I'd like to use. However, the button to turn it on is disabled. I've tried refreshing the page once the Accessibility tab is open but it ...
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1 answer
1k views

Unable to take full page screenshot using "screenshot --fullpage"

I am using Firefox 64.0 on Windows 10 (1803). In past I have been able to take full page screen captures by issuing the command screenshot --fullpage on the browser console. Now using this command ...
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1 answer
245 views

How to manipulate DOM in ubuntu command line without actually rendering the page on the GUI?

I've written a small JS snippet which clicks some buttons in the DOM of a certain target website in a loop. To run this snippet, I open the target website in firefox. Then I paste this JS snippet in ...
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1 answer
125 views

Turn visited website hyperlink to purple

By default any link I visit on google turns purple on most browsers. This only applies to the specific webpages I visit. Is there any way to turn links for all webpages of a particular website purple ...
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1 vote
0 answers
136 views

How to disable the blue lines in Firefox, when developer tools are ON

When we turn on dev tools in Firefox, especially the 'inspector', and we select some element, Firefox marks the element in the main view. This also happens, when we console.log(someHtmlElement) and ...
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3 votes
2 answers
1k views

How to change the width of the columns in Firefox’s developer tools’ network tab

In Chrome, I can customize the width of the columns in its developer tools’ network tab: In Firefox, I can’t figure out how to do the same thing: Is it possible?
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1 vote
1 answer
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Debug video stream in Firefox dev tools

Is it possible to debug a video stream using the Firefox dev tools? Specifially I would like to monitor the transfer rate and find out why a video sometimes stutters. Not sure if it is caused by the ...
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3 votes
0 answers
428 views

Firefox Developer Tools failed to inspect variables on hover over

I have FireFox Quantum 57.0.2 (64 bits) and Windows 8.1. It was working fine till now, but suddenly I can't get pop up value on hover over variables. This and other issues come up in all pages ...
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1 answer
47 views

Disable access to Firefox API in Console

I need to deploy Firefox and prevent users from doing Cu.import calls from the web console. Is this possible at all? If yes, is there a simple way to achieve this setting an about:config pref?
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  • 11
4 votes
1 answer
175 views

Firefox devtools: how to hide console from other dev tabs?

When I open my Firefox 55 devtools (F12), the Console shows up under every tab. Here it's taking up the bottom 40% of the Network Monitor tab: This can be useful if I want to see new console messages ...
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86 views

Show all box models at once sticky [closed]

When I hover a DOM element in the Firefox Developer Tools, margins (yellow) and paddings (purple) are displayed on the website. Is it possible to show these boxes for all elements at once sticky?
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  • 427
1 vote
2 answers
111 views

Change the site's source on each load in Firefox

There's a website on my uni localnet which serves an inline css for body <body class="maincon" style="somejunk"> making it look weird. Removing inline style with the Firefox Inspector (F12) ...
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0 answers
321 views

DownThemAll - Wait page until finish loading then download

I'm using DownThemAll with Firefox. I've several links like this: site1.com/1.html site1.com/2.html site1.com/3.html etc.... I want to download these HTML pages with DownThemAll. The problem is: ...
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1 vote
1 answer
559 views

Inspecting elements on localhost doesn't display element dimensions

I'm using both "Regular" Firefox as well as the Developer edition. At the moment I'm developing a website locally (using node.js/gulp) and am experiencing a weird... maybe a bug? Whenever I ...
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  • 137
3 votes
1 answer
2k views

Firefox Developer Tools - Can't catch POST data

I'm trying to catch the POST requests made after logging into a website using Firefox Developer Tools, but as soon as the page loads and redirects me to the logged in page, all the entries in 'Network'...
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  • 509
4 votes
2 answers
11k views

How to turn on Firefox's Responsive Design Mode's touch simulator?

I want to use Firefox for mobile development. And I would like to turn on Firefox's responsive design's touch simulator. While I'm in device mode in Chrome, the browser shows a gray circle as mouse ...
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2 votes
1 answer
819 views

How to get back the old debugger in Firefox

Firefox 52 introduces a new JavaScript Debugger with new UI but lack of many features that the old one has. One that I found critical and can't work without is the ability to search for some text in ...
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  • 183
0 votes
1 answer
27 views

"Run to line feature" while debugging in Firefox

Is there a run-to-line feature in the default Firefox debugger? I use Firefox on Ubuntu. While debugging a block of code, I right-click on a line hoping to find some option to that effect, instead I ...
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  • 1,765
1 vote
0 answers
110 views

Firefox developer cannot find chrome://ubufox/locale/ubufox.properties

I'm getting an error when I open my firefox developer edition browser in Windows 10, which is that it cannot find chrome://ubufox/locale/ubufox.properties. I suppose the reason is that I have ...
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2 votes
1 answer
1k views

How to disable the grid highlighting of multiple elements in Firefox?

Sorry, I don't know how to name that, tried to search looking for rulers, guides, grid and markup - no luck. I'm speaking about blue dashed lines and the gray area. Usually when you're at inspector ...
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2 votes
4 answers
2k views

Firefox: purge all data (cache, cookies, local storage, etc) for a specific website

Chrome has this handy tool: Lets you purge all kinds of storage for a specific website without ruining your experience for all other websites. How do I do the same in Firefox?
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1 vote
1 answer
44 views

Firefox web-console reference manual available?

In Firefox 46, I was looking for the options available for: The best I can get is this page. I'm actually interested in the full reference of the Firefox console. The best incomplete reference I ...
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1 answer
35 views

Cycling though css values in Firefox's style editor

In Firebug, when editing some css property, I can press up and down to cycle through all the possible values. So if I'm editing the "color" property, and I press up/down, it will cycle through "red", ...
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  • 101
1 vote
0 answers
177 views

Browser color distinction between production and dev environment

I use Firefox to develop and maintain a web application for my office. The interface will look identical for production & development, and the urls won't be easily distinct though except few ...
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3 votes
0 answers
99 views

How do I turn off groupLogMessages in Firefox console, not Firebug?

I know how to do this in Firbug, but want to disable the grouping (red circle with a number in it) in the regular console. I've searched inside about:config, but couldn't find it. Is this possible?
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0 votes
1 answer
80 views

How to set default size of page in firefox developer edition

I use Firefox Developer Edition on my Macbook pro retina. However, Firefox doesn't support finger pinch in and out page enlargement like safari and chrome. I have to do that from top bar. How can I ...
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1 vote
1 answer
320 views

Show autocomplete suggestions for Developer Toolbar in Firefox?

In the screenshot below (Firefox 39), the Developer Toolbar prompt (the one shown on Shift+F2, not the prompt of the (Web) Console raised with Ctrl-Shift-K, which is also shown above the Developer ...
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  • 4,810
0 votes
1 answer
1k views

Firefox about:config reset

I've been troubleshooting my website and I changed a couple of settings in my firefox about:config. I changed the following settings, And now I get a ton of these errors on my site, These errors ...
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1 vote
2 answers
2k views

I am having trouble overriding Firefox default css using userContent.css file

I am using Ubuntu 14.10 with dark theme , Today I have upgraded my firefox to developer edition (40.x) previously i was on firefox 38.x I use some of the sites where firefox default from.css styling ...
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