What's New In DevTools (Chrome 80)

Support for let and class redeclarations in the Console

The Console now supports redeclarations of let and class statements. The inability to redeclare was a common annoyance for web developers who use the Console to experiment with new JavaScript code.

For example, previously, when redeclaring a local variable with let, the Console would throw an error:

Now, the Console allows the redeclaration:

Chromium issue #1004193

Improved WebAssembly debugging

DevTools has started to support the DWARF Debugging Standard, which means increased support for stepping over code, setting breakpoints, and resolving stack traces in your source languages within DevTools. Check out Improved WebAssembly debugging in Chrome DevTools for the full story.

Network panel updates

Request Initiator Chains in the Initiator tab

You can now view the initiators and dependencies of a network request as a nested list. This can help you understand why a resource was requested, or what network activity a certain resource (such as a script) caused.

After logging network activity in the Network panel, click a resource and then go to the Initiator tab to view its Request Initiator Chain:

• The inspected resource is bold. In the screenshot above, https://web.dev/default-627898b5.js is the inspected resource.
• The resources above the inspected resource are the initiators. In the screenshot above, https://web.dev/bootstrap.js is the initiator of https://web.dev/default-627898b5.js. In other words, https://web.dev/bootstrap.js caused the network request for https://web.dev/default-627898b5.js.
• The resources below the inspected resource are the dependencies. In the screenshot above, https://web.dev/chunk-f34f99f7.js is a dependency of https://web.dev/default-627898b5.js. In other words, https://web.dev/default-627898b5.js caused the network request for https://web.dev/chunk-f34f99f7.js.

Chromium issue #842488

Highlight the selected network request in the Overview

After you click a network resource in order to inspect it, the Network panel now puts a blue border around that resource in the Overview. This can help you detect if the network request is happening earlier or later than expected.

Chromium issue #988253

URL and path columns in the Network panel

Use the new Path and URL columns in the Network panel to see the absolute path or full URL of each network resource.

Right-click the Waterfall table header and select Path or URL to show the new columns.

Chromium issue #993366

Updated User-Agent strings

DevTools supports setting a custom User-Agent string through the Network Conditions tab. The User-Agent string affects the User-Agent HTTP header attached to network resources, and also the value of navigator.userAgent.

The predefined User-Agent strings have been updated to reflect modern browser versions.

To access Network Conditions, open the Command Menu and run the Show Network Conditions command.

Chromium issue #1029031

Audits panel updates

New configuration UI

The configuration UI has a new, responsive design, and the throttling configuration options have been simplified. See Audits Panel Throttling for more information on the throttling UI changes.

Coverage tab updates

Per-function or per-block coverage modes

The Coverage tab has a new dropdown menu that lets you specify whether code coverage data should be collected per function or per block. Per block coverage is more detailed but also far more expensive to collect. DevTools uses per function coverage by default now.

Coverage must now be initiated by a page reload

Toggling code coverage without a page reload has been removed because the coverage data was unreliable. For example, a function can be reported as unused if its execution was a long time ago and V8's garbage collector has cleaned it up.

Chromium issue #1004203

Feedback

To discuss the new features and changes in this post, or anything else related to DevTools:

• File definite bug reports and feature requests at Chromium Bugs.
• Discuss possible features, changes, and bugs on the Mailing List.
• Get help on how to use DevTools on Stack Overflow.
• Tweet us at @ChromeDevTools.
• File bugs on this document in the Web Fundamentals repository.

Consider Canary

If you're on Mac or Windows, consider using Chrome Canary as your default development browser. Canary gives you access to the latest DevTools features.

Note: Canary is released as soon as its built, without testing. This means that Canary breaks about once-a-month. It's usually fixed within a day. You can go back to using Chrome Stable while Canary is broken.

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