What's new in DevTools, Chrome 140

Sofia Emelianova
Sofia Emelianova
GitHub

Debug more insights with Gemini

In Performance > Insights, you can now click Debug with AI (previously Ask AI) to chat and debug with Gemini in the AI assistance panel more performance insights:

  • Improve image delivery
  • Legacy JavaScript
  • Duplicated JavaScript
  • Modern HTTP

The before and after adding the 'Debug with AI' button to more performance insights.

Emulate the 'Save-Data' header in 'Network conditions'

In the Network conditions panel, you can now emulate the behaviour of the Save-Data request header. This header is a network client hint which indicates the client's preference for reduced data usage. It's also available through the navigator.connection.saveData API.

The before and after adding the 'Save-Data' request header emulation to 'Network conditions'.

Chromium issue: 40668980.

See the Baseline status in a CSS property tooltip

In Elements > Styles, when you hover over any CSS property, you can now see, under the property's definition, its availability across major browsers according to its Baseline status.

The before and after adding the Baseline status to the CSS property tooltips.

Chromium issue: 417749762.

Override form factors in user agent client hints

In the Network conditions > User agent client hints drop-down, you now have options to override form factors, specifically, the values of the Sec-CH-UA-Form-Factors request header.

The before and after adding the options for form factor override to user agent client hints.

Chromium issue: 422218341.

Lighthouse 12.8.0

The Lighthouse panel now runs Lighthouse 12.8.0.

Most notably in this version, Lighthouse adds a new report: Mitigate DOM-based XSS with trusted types.

See also the full list of changes.

To learn the basics of using the Lighthouse panel in DevTools, see Lighthouse: Optimize website speed.

Chromium issue: 40543651.

Miscellaneous highlights

These are some of many notable fixes and improvements in this release:

  • AI assistance:
    • Chat history is now cleared when you disable the corresponding AI feature in Settings.
    • Accessibility: Screen readers now announce context titles early, "Answer loading" when the answer starts streaming and "Answer ready" when the answer is complete.
  • Elements:
    • The Styles tab can now evaluate sibling-index(), sibling-count(), and env() CSS functions (crbug.com/417128001, crbug.com/40196710).
    • Added support for ::view-transition-group-children pseudo element (crbug.com/425901164).
    • Added support for accessibility issues about interactive content in the <summary> element (crbug.com/427172874).
    • From the Computed tab, you can now navigate to longhand properties in Styles (crbug.com/41486012).
    • Easing, Color editors: You can now interact with bezier swatches for animation transitions and color swatches using the keyboard (crbug.com/401213421).
  • Network: HAR files import now also includes request and response cookies (crbug.com/432995868).
  • Device mode: Updated user agents for Apple devices to latest Safari 18.5.

Download the preview channels

Consider using the Chrome Canary, Dev, or Beta as your default development browser. These preview channels give you access to the latest DevTools features, let you test cutting-edge web platform APIs, and help you find issues on your site before your users do!

Get in touch with the Chrome DevTools team

Use the following options to discuss the new features, updates, or anything else related to DevTools.

What's new in DevTools

A list of everything that has been covered in the What's new in DevTools series.