What's New In DevTools (Chrome 78)

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Multi-client support in the Audits panel #

You can now use the Audits panel in combination with other DevTools features like Request Blocking and Local Overrides.

For example, suppose that your Audits panel report says that your page's performance score is 70 and one of your biggest performance opportunities is eliminating render-blocking resources.

The initial Performance score is 70.

Figure 1. The initial Performance score.

The initial report says that 3 render-blocking scripts are an issue.

Figure 2. The initial report says that 3 render-blocking scripts are an issue.

Now that the Audits panel can be used in combination with request blocking, you can quickly measure how much the render-blocking scripts affect your load performance by first blocking the requests for the render-blocking scripts:

Using the Request Blocking tab to block the problematic scripts.

Figure 3. Using the Request Blocking tab to block the problematic scripts.

And then auditing the page again:

The Performance score improved to 97 after enabling request blocking.

Figure 4. The Performance score improved to 97 after blocking the problematic scripts.

You could alternatively use Local Overrides to add async attributes to each of the script tags, but "we'll leave that as an exercise for the reader." Go to Multi-client demo to try it out. Or check out this tweet for a video demonstration.

Chromium issue #991906

Payment Handler debugging #

The Background Services section of the Application panel now supports Payment Handler events.

  1. Go the the Application panel.

  2. Open the Payment Handler pane.

  3. Click Record. DevTools records Payment Handler events for 3 days, even when DevTools is closed.

    Recording Payment Handler events.

    Figure 5. Recording Payment Handler events.

  4. Enable Show events from other domains if your Payment Handler events occur on a different origin.

  5. After triggering a Payment Handler event, click the event's row to learn more about the event.

    Viewing a Payment Handler event.

    Figure 6. Viewing a Payment Handler event.

Chromium issue #980291

Lighthouse 5.2 in the Audits panel #

Note: This actually launched in Chrome 77, but we missed it in the last release notes so we're covering it now.

The Audits panel is now running Lighthouse 5.2. The new Third-Party Usage diagnostic audit tells you how much third-party code was requested and how long that third-party code blocked the main thread while the page loaded. See Optimize your third-party resources to learn more about how third-party code can degrade load performance.

A screenshot of the 'Third-Party Usage' audit in the Lighthouse report UI.

Figure 7. The Third-party usage audit.

Chromium issue #772558

Largest Contentful Paint in the Performance panel #

When analyzing load performance in the Performance panel, the Timings section now includes a marker for Largest Contentful Paint (LCP). LCP reports the render time of the largest content element visible in the viewport.

The LCP marker in the Timings section.

Figure 8. The LCP marker in the Timings section.

To highlight the DOM node associated with LCP:

  1. Click the LCP marker in the Timings section.

  2. Hover over the Related Node in the Summary tab to highlight the node in the viewport.

    The Related Node section of the Summary tab.

    Figure 9. The Related Node section of the Summary tab.

  3. Click the Related Node to select it in the DOM Tree.

File DevTools issues from the Main Menu #

If you ever encounter a bug in DevTools and want to file an issue, or if you ever get an idea on how to improve DevTools and want to request a new feature, go to Main Menu > Help > Report a DevTools issue to create an issue in the DevTools engineering team's tracker. Providing a minimal, reproducible example on Glitch dramatically increases the team's ability to fix your bug or implement your feature request!

Main Menu > Help > Report a DevTools issue.

Figure 10. Main Menu > Help > Report a DevTools issue.

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