Chrome 92 — What’s New In DevTools

New in DevTools that ship with Chrome 92 (selection):

What’s New In DevTools (Chrome 92) →

Chrome 91 – What’s New in DevTools

That CSS Scroll-Snap highlighter sure is one very welcome addition!

What’s New In DevTools (Chrome 91) →

Identify and Extract Pseudo-Element Selectors from built-in HTML Elements using DevTools

Recently Stefan Judis shared how to style the browse button of a file selector using the ::file-selector-button pseudo-element

But what about other complex elements in the browser? How can we tweak individual parts of those? Take <audio> for example: is there a pseudo-element we can use to style the play button?


Table of Contents

  1. Dissecting <input type="file" />
  2. How to use DevTools to peek inside <input type="file" />
  3. Dissecting <audio>
  4. Is there a catch?
  5. One last thing


# Dissecting <input type="file" />

Before we answer the question above, let’s first take a look at the <input type="file" /> Stefan used. Below is screenshot of how it’s rendered in Chromium on Mac, with a few extra outlines added.

Even though we only type 1 element in our HTML code, we see it consists of two parts:

  1. A “Choose File” button
  2. A label reading “No file chosen”

Internally, this is also how the browser builds it. We type in:

<input type="file" />

But what’s being rendered is this:

<input type="button" value="Choose file" pseudo="-webkit-file-upload-button" id="file-upload-button">
<span aria-hidden="true">No file chosen</span>

(I’ll show you further down this post how I know this 😉)

The ::file-selector-button selector Stefan mentioned targets only the <input type="button" …> you see there. Using it you can style the button, like he did.

🧐 If you’re paying close attention you might notice that the pseudo-element used is ::file-selector-button, whilst the pseudo attribute of the button reads -webkit-file-upload-button. More on that further down the post 😉


# How to use DevTools to peek inside <input type="file" />

In the Chromium DevTools we don’t get to see the two elements that make up <input type="file" />. That’s because this information as is hidden in the Shadow DOM.

Thankfully there is a way to have DevTools show them. To do so, open DevTools’ Settings, and under Elements check the option that reads “Show user agent Shadow DOM”.

🦊 Firefox or 🧭 Safari user? The DevTools in Firefox/Safari have this option enabled out of the box.

Once enabled you’ll see #shadow-root (user-agent) appear in the Elements Tree for all elements that are built that way (and there quite a few!).

<input type="file">
  ↳ #shadow-root (user-agent)
      <input type="button" value="Choose file" pseudo="-webkit-file-upload-button" id="file-upload-button">
      <span aria-hidden="true">No file chosen</span>

☝️ Having this option enabled all the time can be quite distracting. I personally only turn it on when I need it.


# Dissecting <audio>

Winging back to our initial question “is there a pseudo-element we can use to style the play button?”, we can use the DevTools to see the underlying structure.

In Chromium we get back this structure:

<audio controls="" src="/media/cc0-audio/t-rex-roar.mp3">
  ↳ #shadow-root (user-agent)
    <div pseudo="-webkit-media-controls" class="phase-ready state-stopped">
      <div pseudo="-webkit-media-controls-overlay-enclosure">
        <input pseudo="-internal-media-controls-overlay-cast-button" type="button" aria-label="play on remote device" style="display: none;">
      <div pseudo="-webkit-media-controls-enclosure">
        <div pseudo="-webkit-media-controls-panel">
          <input type="button" pseudo="-webkit-media-controls-play-button" aria-label="play" class="pause" style="">
          <div aria-label="elapsed time: 0:00" pseudo="-webkit-media-controls-current-time-display" style="">0:00</div>
          <div aria-label="total time: / 0:02" pseudo="-webkit-media-controls-time-remaining-display" style="">/ 0:02</div>
          <input type="range" step="any" pseudo="-webkit-media-controls-timeline" max="2.115918" aria-label="audio time scrubber 0:00 / 0:02" aria-valuetext="elapsed time: 0:00">
          <div pseudo="-webkit-media-controls-volume-control-container" class="closed" style="">
            <div pseudo="-webkit-media-controls-volume-control-hover-background"></div>
            <input type="range" step="any" max="1" aria-valuemax="100" aria-valuemin="0" aria-label="volume" pseudo="-webkit-media-controls-volume-slider" aria-valuenow="100" class="closed" style=""><input type="button" pseudo="-webkit-media-controls-mute-button" aria-label="mute" style="">
          <input type="button" pseudo="-webkit-media-controls-fullscreen-button" aria-label="enter full screen" style="display: none;">
          <input type="button" aria-label="show more media controls" title="more options" pseudo="-internal-media-controls-overflow-button" style="">
      <div role="menu" aria-label="Options" pseudo="-internal-media-controls-text-track-list" style="display: none;"></div>
      <div pseudo="-internal-media-controls-overflow-menu-list" role="menu" class="closed" style="display: none;">
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label=" Play " style="display: none;">
          <input type="button" pseudo="-webkit-media-controls-play-button" tabindex="-1" aria-label="play" class="pause" style="display: none;">
          <div aria-hidden="true">
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label="enter full screen Full screen " style="display: none;">
          <input type="button" pseudo="-webkit-media-controls-fullscreen-button" aria-label="enter full screen" tabindex="-1" style="display: none;">
          <div aria-hidden="true">
            <span>Full screen</span>
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label="download media Download " class="animated-0" style="">
          <input type="button" aria-label="download media" pseudo="-internal-media-controls-download-button" tabindex="-1" style="">
          <div aria-hidden="true">
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label=" Mute " class="animated-2" style="display: none;">
          <input type="button" pseudo="-webkit-media-controls-mute-button" tabindex="-1" aria-label="mute" style="display: none;">
          <div aria-hidden="true">
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label="play on remote device Cast " class="animated-1" style="display: none;">
          <input pseudo="-internal-media-controls-cast-button" type="button" aria-label="play on remote device" tabindex="-1" style="display: none;">
          <div aria-hidden="true">
        <label pseudo="-internal-media-controls-overflow-menu-list-item" role="menuitem" tabindex="0" aria-label="show closed captions menu Captions " class="animated-0" style="display: none;">
          <input aria-label="show closed captions menu" type="button" pseudo="-webkit-media-controls-toggle-closed-captions-button" tabindex="-1" style="display: none;">
          <div aria-hidden="true">

Or visually, with outlines added:

With a bit of digging we can find the the play button on line #9, and extract its pseudo attribute.

<input type="button" pseudo="-webkit-media-controls-play-button" aria-label="play" class="pause" style="">

👉 To style the play button we can use ::-webkit-media-controls-play-button


# Is there a catch?

While the ::-webkit-media-controls-play-button selector above works, there’s a catch though: it only works in Chromium based browsers, and this for several reasons:

  1. Every browser engine has its own implementation for what makes up an <audio> element. Shown below is a comparison of the UI for the <audio> as seen in Firefox, Chromium, and Safari.

    Whilst all implementation contain a play button, not all — for example — contain an element that indicates the current time. Styling that wouldn’t be possible.

  2. Not all browser expose the same parts of the UI using pseudo-elements. When it comes to <audio> for example, only Chromium exposes parts of its UI. Firefox and Safari don’t expose any pseudo-element for <audio>

    And even if they would, the wouldn’t use ::-webkit-media-controls-play-button for it.

Another aspect to take into account is that ::-webkit-media-controls-play-button is something that Chromium decided to use. This wasn’t discussed with any other browser vendor. As Thomas Steiner warns:


# One last thing

To close off I still owe you an explanation to why Chromium lists ::-webkit-file-upload-button for the browse button of <input type="file" />, instead of ::file-selector-button.

This is because they first exposed it using their own internal ::-webkit-file-upload-button name. It was only later that the CSS Working Group decided to standardize it to ::file-selector-button.


Did this help you out? Like what you see?
Thank me with a coffee.

I don't do this for profit but a small one-time donation would surely put a smile on my face. Thanks!

☕️ Buy me a Coffee (€3)

To stay in the loop you can follow @bramus or follow @bramusblog on Twitter.

Debug/Inspect z-index stacking with the “CSS Stacking Context Inspector” DevTools extension

The Stacking Contexts Inspector is a DevTools extension for Google Chrome that allows you to analyse the stacking contexts available on a webpage. This extension will add a new panel to the DevTools and a new sidebar on the elements panel.

Handy for when you’re having stacking issues.

CSS Stacking Context Inspector →
Stacking Contexts Inspector →

☝️ If you’re running “Edgium”, you can use it’s built-in 3D View to visualize the stacking contexts.

Hat tip, Josh!

Debugging Layout Shifts

Over at, Katie Hempenius learns us how to identify and fix layout shifts using the Layout Instability API and the DevTools.

What I take away from this is that you can easily spot them using DevTools: In the Rendering Panel you can enable an option to highlight areas of Layout Shift:

To enable Layout Shift Regions in DevTools, go to Settings → More Tools → Rendering → Layout Shift Regions then refresh the page that you wish to debug. Areas of layout shift will be briefly highlighted in purple.

Debugging layout shifts →

Inspecting Safari on iPhone using the Safari (on desktop) DevTools

Harry Roberts explains how to inspect pages from MobileSafari (on your iDevice) using the Safari (on your Mac) DevTools.

It’s been a while since I’ve done this, but if I recall correctly you can — once set up — also debug pages in MobileSafari without needing a physical USB connection. It’ll run over Bluetooth.

Measuring Network Performance in Mobile Safari →

Chrome 88 – What’s New in DevTools

I especially like the New CSS Angle Visualization Tool 🙂

What’s New In DevTools (Chrome 88) →

Chrome DevTools Pong – A game to play inside the Chrome DevTools

Move over Chrome Dino Game! Now you can play Pong inside the Chrome DevTools.

Chrome DevTools Pong →

Spoiler: How it works

In case you were wondering: it’s a regular Pong game, but with the elements visually hidden (opacity: 0;) so that they only show up in the DevTools’ Layers Panel.

So simple, that becomes awesome!

Reactime – A time-travel state debugger for React apps

Reactime is a debugging tool for React developers. It records state whenever it is changed and allows the user to jump to any previously recorded state.

This dev tool is for React apps using stateful components and prop drilling, and has beta support for Context API, conditional state routing, Hooks (useState, useEffect) and functional components.

Here’s a demo of it in action:

Comes in two parts: a Chrome Extension and a NPM package that you need to install inside your project.

npm i reactime

You’ll also need perform some (upfront) code adjustments so that the package sends data over to the extension:

import reactime from 'reactime';

const rootContainer = document.getElementById('root');
ReactDOM.render(, rootContainer);


To support concurrent mode, you’ll need this adjustment:

import reactime from 'reactime';

const rootContainer = ReactDOM.createRoot(document.getElementById('root'));

Reactime →

💡 Be sure to also check out the “regular” React DevTools. They’re awesome!

Emulate Dark Mode using Chrome DevTools

Coming to the next version of Chrome is a way to emulate “Dark Mode” using the DevTools. With the DevTools open and focused, hit SHIFT+CMD+P and choose “Emulate CSS prefers-color-scheme: dark from the menu

You can also access the option via the Rendering panel.