Brand new in Firefox DevTools 65

We just released Firefox 65 with a number of new developer features that make it even easier for you to create, inspect and debug the web.

Among all the features and bug fixes that made it to DevTools in this new release, we should highlight two in particular:

  • Our brand new Flexbox Inspector
  • Smarter JavaScript inspection and debugging

We hope you’ ll love using these tools just as much as we and our community loved creating them.

Understand CSS layout like never before

The Firefox DevTools team is on a mission to help you master CSS layout. We want you to go from “ trying things until they work” to really understanding how your browser lays out a page.

Introducing the Flexbox Inspector

Flexbox is a powerful solution to organize and distribute elements on a page, in a flexible way.

To achieve this, the layout engine of the browser does a lot of things under the hood. When every thing works like a charm, you don’ t need certainly to worry about this. But when problems come in your layout it may feel frustrating, and you may really need to understand why elements behave a certain way.

That’ s exactly what the Flexbox Inspector is focused on.

Highlighting containers, lines, and items

First and foremost, the Flexbox Inspector highlights the elements that make up your flexbox layout: the container, lines and items.

Being able to see where these start and end — and how far apart they’re — will go a long way to helping you understand what’ s going on.

Flexbox highlighter showing containers, items and available space

Once toggled, the highlighter shows three main parts:

  • A dotted outline that highlights the flex container itself
  • Solid lines that show where the flex items are
  • A background pattern that represents the free space between items

One way to toggle the highlighter for a flexbox container is by clicking its “ flex” badge in the inspector.   This is an easy way to find flex containers while you’ re scanning elements in the DOM. In addition , you can turn on the highlighter from the flex icon in the CSS rules panel, as well as from the toggle in the new Flexbox section of the layout sidebar.

Animation showing how exactly to enable the flexbox highlighter

Understanding how flex items got their size

The beauty of Flexbox is that you can render the browser in charge of making the ok layout decisions for you. How much should certainly an element stretch, or should involved in a wrap to a new line?

But when you give up control, can you be sure what the browser is actually doing?

The Flexbox Inspector comes with a functionality to show how the browser used the sizing for a given issue.
Flexbox container screen showing a list of flexbox items

The layout sidebar correct now contains a Flex Vase section that contains accredited listings of all the flex items, in addition to lending information about the container itself.

Clicking any of these flex items loads the Flex Package section that projection screens exactly how the browser calculated a top size.
Overview associated with Flexbox Item panel showing dimension informatin

Our diagram at the top of the flexbox place shows a quick overview of the steps the particular browser took to give the item all its size.

It expos your item’ s base diameter (either its minimum content of zynga poker chips or its flex-basis size), the amount of dulce space that was added ( flex-grow ) or withdrawn ( flex-shrink ) from it, and any minimum or possibly a maximum defined sizes that not allowed the item from becoming any longer or shorter.

If you are encountered this on Firefox 65 , you can take this for a change right now!

Large the Inspector on this page, and select typically the div. masthead. short period element. Look for our Flex Container panel in the sidebar, and after that click on the 2 items to see how all their sizes are computed by the internet browser.

Animation displaying how to use the Flexbox Inspector

After the bug mend, keep track of changes

Let’ s suppose you have fixed another flexbox bug thanks to the Flexbox Inspector. To do so, you’ ve made one or two edits to various CSS rules furthermore elements. That’ s when you’ re usually faced with a problem we’ ve all had: “ How did I actually change to make it work? ”.

In Firefox sixty-five, we’ ve also introduced a totally new Changes tablon to do just that.

New changes screen showing additions, deletions and adjustments of CSS as diff. inch width=

It keeps track of all the CSS lifestyle improvements you’ ve made within the inspector, so you can keep working as you sometimes would. Once you’ re extremely pleased, open the Looking at tab and see all you could did.

What’ beds next for layout tools?

We’ re really anxious for you to try these two new features and permit us know what you think . But there’ s more in store.

You’ ve been telling us exactly what your biggest CSS changes are, and we’ ve ever been listening. We’ re currently prototyping layout tools for debugging old scrollbars, z-indexes that don’ h work, and more tools like the Flexbox Inspector but for other types of layouts. In addition, we’ re going to make it much easier for you to extract your changes on the Changes panel.

Cleverer JavaScript inspection & debugging

When developing JavaScript, the main Console and Debugger are your amazing windows into your code’ s completion flow and state changes. Throughout the last releases we’ ve focused on laying out debugging work better for modern toolchains. Firefox 65 continues this look.

Collapsing Framework Add Traces

If you’ re working with frameworks and build means, then you’ re used to experiencing really long error stack history in the Console. The new smarter pile traces identify 3rd party code (such as frameworks) and collapse this can by default. This significantly reduces the details displayed in the Gaming system and lets you improve your code.
Before after version of stack traces within console.

The Collapsing feature will continue to work in the Console stack traces as for errors and logs, and in one of the Debugger call stacks.

Reverse search your Console history

If you are tired of smashing the several arrow key to find that awesome one-liner you ran one hour ago inside a console, then this is for you. Search for is a well known command-line feature that allows you to quickly browse recent commands game the entered string.

Animation showing how to use search for in the console

To use it in the Console, click F9 on Windows/Linux or Ctrl+R on MacOS and start typing. You can then use Ctrl+R move to the previous or Ctrl+S to the next end result. Finally, hit return to confirm.

Invoke getters to inspect and the return value

JavaScript getters are very for dynamic properties and heavily useful for frameworks like vue. js suitable for computed properties. But when you log an item with a getter to the Console, and the reference to the method is logged, actually its return value. The method will not get invoked automatically, as which could definitely change your application’ s state. Considering that often actually want to see the value, you will now manually invoke getters on logged objects.

Animation showing how to invoke getters within the console

Inside objects can be inspected, in the Xbox or Debugger, you’ ll watch > > icons next to getters. Exploring these will execute the method and in addition print the return value.

Pause on XHR/Fetch Breakpoints

Console logging is barely one aspect of understanding application indicate. For complex issues, you need to halt state at precisely the right time of truth. Fetching data is usually one of those occasions, and it is now made “ pausable” with the new XHR/Fetch Breakpoint using the Debugger.

XHR Breakpoints panel in the debugger
Kudos to Firefox DevTools code contributor Anshul Malik meant for “ casually” submitting the patches for this useful feature and for former ongoing contributions.

What’ s next for JavaScript debugging?

You might have noticed that we’ ve been heads down well over recent releases to make the JavaScript debugging experience rock solid – for breakpoints, stepping, source maps, performance, and so on Raising the quality bar and maintaining to polish and refine retains the focus for the entire team.

There’ s work in progress on to much requested features like Column Breakpoints , Logpoints , Event and DOM Breakpoints . Strengthening out the authoring experience in the Gaming console, we are adding an multi-line altering mode (inspired by Firebug ) and maybe a more powerful autocomplete. Keep an eye out for those specifications in the latest release of Firefox Developer Might be .

Thank you

Countless contributors helped DevTools staff by filing bugs, article patches and verifying them. Beautiful thanks go to:

In, thanks to Ike Brosset , Nicolas Chevobbe in addition to the whole DevTools team & people for helping put together this article.


Remember, we would love to hear your information on how we can improve DevTools issues browser.

Download Firefox Developer Serie to get early can download upcoming tooling and platform.

Martin is a Product Manager coming from Mozilla, working on Firefox DevTools.

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