Lighthouse 2.6 Updates

Lighthouse 2.6 is out! Highlights include:

See the 2.6 release notes for the full list of new features, changes, and bug fixes.

How to update to 2.6

  • NPM. Run npm update lighthouse. Run npm update lighthouse -g flag if you installed Lighthouse globally.
  • Chrome Extension. The extension should automatically update, but you can manually update it via chrome://extensions.
  • DevTools. The Audits panel will be shipping with 2.6 in Chrome 65. You can check what version of Chrome you're running via chrome://version. Chrome updates to a new version about every 6 weeks. You can run the latest Chrome code by downloading Chrome Canary.

New performance audits

JavaScript boot-up time is high

View a breakdown of the time your page spends parsing, compiling, and executing each script. JavaScript boot-up time is a somewhat-hidden but important factor in page load time.

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Figure 1. The JavaScript boot-up time is high audit

Uses inefficient cache policy on static assets

Make sure that the browser properly caches each of your resources.

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Figure 2. The Uses inefficient cache policy on static assets audit

Avoids page redirects

Page redirects add an extra network roundtrip, or two if an extra DNS lookup is required. Minimize redirects in order to speed up page load time.

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Figure 3. The Avoids page redirects audit

Rehaul of the accessibility section score

In Lighthouse 2.6, the aggregate accessibility score is calculated differently. The score weighs each accessibility audit based on the severity of its impact on user experience, as well as the frequency of the issue, based on the HTTP Archive dataset. See googlechrome/lighthouse/issues/3444 for an in-depth discussion.

Report UX Improvements

Top-level errors

At the top of your report, Lighthouse alerts you to errors that may have affected your page's scores.

Top-level errors at the top of a report
Figure 4. Top-level errors at the top of a report

Print summary and expanded views

Click Export Report Export Report then select Print Summary or Print Expanded to print out summarized or detailed versions of your reports.

Print summary and expanded views
Figure 5. Print summary and expanded views

Aspect ratio bug fix

2.6 also fixes a bug that caused the Displays images with correct aspect ratio audit to fail even when there were no images on the page, or all images were properly sized.