Demolish the web with the Firefox Dev Tools!

Daniele Scasciafratte, Mozilla Reps, Co Founder/CTO Codeat

Demolish the web with the Firefox Dev Tools

Daniele Scasciafratte @Mte90Net, Mte90.Net

It's me, Mario ehm Daniele!


How it's done?


Destroy it


It allows you to interact with the DOM, and the page itself, execute and study JavaScript.
Avalaible also for Google Chrome and as a JavaScript snippet.
Slows the browser and is not integrated natively

Obsolete! Retired!

Firefox Developer Edition

Show me the settings!

We want rules ehm ruler!

Demo time


Ctrl + Shift + I or left button "Inspect element"
Daniele, Don't forget to show the contextual menu!

Useless Rules

jQuery events

The tooltip show the Javascript code and not the wrapper generated from jQuery

Screenshot the selected node

JSON Source View

Filter Editor

CSS Docs tooltip

Save your fingers from search and click on Google!

Switch unit size

Drag & Drop the DOM

Right menu

Highlight all elements by selector

Grid Tool

Animation Editor

Animation proprierty

Geometry Editor

Cubic Bezier Editor

Toggle CSS class

Style Editor

Support for VIM/Emacs/Sublime Text

On about:config set devtools.editor.keymap as vim or emacs or sublime text

SourceMaps Support

Responsive View

Media query

Network Throttling


Tips for the console

If you have an element currently selected in your Inspector, you can use the reference $0 to call it within your code. For example, to see the elements' contents you would type $0.innerHTML.
For previous you can use temp0 and so on.

To access to the document.querySelectorAll you can use $$.
To access to the document.querySelector you can use $.
To access to the previous value returned in console $_.

To copy the HTML of object you can use copy($0).
To inspect an object inspect($0).

JavaScript Errors

JavaScript Debugger

Debugger method

Network Stack Trace

Compare perfomance of cache vs no-cache




Tool's Extensions



DevTools Reload


debugger.html is a hackable debugger for modern times, built from the ground up using React and Redux.

Mozilla created this debugger for use in the Firefox Developer Tools. We hope to not only to create a great debugger that works with the Firefox and Chrome Debugging Protocol but development community that can embed this debugger in your own projects with tools like NPM.


WebAssebly Explorer


Daniele Scasciafratte | @Mte90Net | Slides: