What's New In DevTools (Chrome 77)

Technical Writer, Chrome DevTools & Lighthouse

Copy element's styles

Right-click a node in the DOM Tree to copy that DOM node's CSS to your clipboard.

Copy styles. — Figure 1. Copy element styles.

Thanks Adam Argyle and VisBug for the inspiration.

Visualize layout shifts

Supposing you're reading a news article on your favorite website. As you're reading the page, you keep losing your place because the content is jumping around. This problem is called layout shifting. It usually happens when images and ads finish loading. The page hasn't reserved any space for the images and ads, so the browser has to shift all the other content down to make room for them. The solution is to use placeholders.

DevTools can now help you detect layout shifting:

Open the Command Menu.
Start typing Rendering.
Run the Show Rendering command.
Enable the Layout Shift Regions checkbox. As you interact with a page, layout shifts are highlighted blue.

Chromium issue #961846

Lighthouse 5.1 in the Audits panel

The Audits panel is now running Lighthouse 5.1. New audits include:

Provides a valid apple-touch-icon. Checks that a PWA can be added to an iOS homescreen.
Keep request counts and file sizes low. Reports the total number of network requests and file sizes for various categories, such as documents, scripts, stylesheets, images, and so on.
Maximum Potential First Input Delay. Measures the maximum potential time between a user's first page interaction and the browser's response to that interaction. Note that this metric replaces the Estimated Input Latency metric. Maximum Potential First Input Delay does not factor into your Performance category score.

The Node and CLI versions of Lighthouse 5.1 have 3 new major features worth checking out:

Performance Budgets. Prevent your site from regressing over time by specifying request counts and file sizes that pages should not exceed.
Plugins. Extend Lighthouse with your own custom audits.
Stack Packs. Add audits tailored to specific technology stacks. The WordPress Stack Pack shipped first. React and AMP Stack Packs are in development.

OS theme syncing

If you're using the dark theme of your OS, DevTools now switches to its own dark theme automatically.

Keyboard shortcut for opening the Breakpoint Editor

Press Control+Alt+B or Command+Option+B (Mac) when focused in the Sources panel's Editor to open the Breakpoint Editor. Use the Breakpoint Editor to create Logpoints and Conditional Breakpoints.

Prefetch cache in Network panel

The Size column of the Network panel now says (prefetch cache) when a resource was loaded from the prefetch cache. Prefetch is a new-ish web platform feature for speeding up subsequent page loads. Can I use... reports that it's supported in 83.33% of global browsers as of July 2019.

The Size column showing that resources came from the prefetch cache. — Figure 5. The **Size** column shows that `prefetch2.html` and `prefetch2.css` came from `(prefetch cache)`.

See Prefetch Demo to try it out.

Chromium issue #935267

Private properties when viewing objects

The Console now shows private class fields in its object previews.

When inspecting an object, the Console now shows private fields like '#color'. — Figure 6. The old version of Chrome on the left does not show the `#color` field when inspecting the object, whereas the new version on the right does.

Notifications and push messages in the Application panel

The Background Services section of the Application panel now supports Push Messages and Notifications. Push Messages occur when a server sends information to a service worker. Notifications occur when a service worker or page script shows information to the user.

As with the Background Fetch and Background Sync features from Chrome 76, once you start recording, Push Messages and Notifications on this page are recorded for 3 days, even when the page is closed, and even when Chrome is closed.

The new Notifications and Push Messages panes. — Figure 7. The new Push Messages and Notifications panes in the Application panel.

Chromium issue #927726

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