New features and major changes coming to DevTools in Chrome 66 include:
- Blackboxing in the Network panel
- Auto-adjust zooming in Device Mode
- Pretty-printing in the Preview and Response tabs
- Previewing HTML content in the Preview tab
- Local Overrides with styles inside of HTML
Read on, or watch the video version of the release notes below.
Blackboxing in the Network panel
Previously, if your framework wrapped network requests in a wrapper, the Initiator column wouldn't be that helpful. All network requests pointed to the same line of wrapper code.
What you really want in this scenario is to see the application code that causes the request. That's now possible:
- Hover over the Initiator column. The call stack that caused the request appears in a pop-up.
- Right-click the call that you want to hide from the initiator results.
- Select Blackbox script. The Initiator column now hides any calls from the script that you blackboxed.
Manage your blackboxed scripts from the Blackboxing tab in Settings.
See Ignore a script or pattern of scripts to learn more about blackboxing.
Pretty-printing in the Preview and Response tabs
The Preview tab in the Network panel now pretty-prints resources by default when it detects that those resources have been minified.
To view the unminified version of a resource, use the Response tab. You can also manually pretty-print resources from the Response tab, via the new Format button.
Previewing HTML content in the Preview tab
Previously, the Preview tab in the Network panel showed the code of an HTML resource in certain situations, while rendering a preview of the HTML in others. The Preview tab now always does a basic rendering of the HTML. It's not intended to be a full browser, so it may not display HTML exactly as you expect. If you want to see the HTML code, click the Response tab, or right-click a resource and select Open in Sources panel.
Auto-adjust zooming in Device Mode
When in Device Mode, open the Zoom dropdown and select Auto-adjust zoom to automatically resize the viewport whenever you change device orientation.
Local Overrides now works with some styles defined in HTML
Back when DevTools launched Local Overrides in Chrome 65, one limitation was that it
couldn't track changes to styles defined within HTML. For example, in Figure 7 there's a
style rule in the
head of the document that declares
font-weight: bold for
In Chrome 65, if you changed the
font-weight declaration via the DevTools Style pane,
Local Overrides wouldn't track the change. In other words, on the next reload, the
style would revert back to
font-weight: bold. But in Chrome 66, changes like this now persist
across page loads.
Bonus tip: Blackbox framework scripts to make Event Listener Breakpoints more useful
viewers commented that event listener breakpoints aren't useful for apps built on top of
frameworks, because the event listeners are often wrapped in framework code. For example, in
Figure 8 I've set up a
click breakpoint in DevTools. When I click the button in the demo,
DevTools automatically pauses in the first line of listener code. In this case, it
pauses in Vue.js's wrapper code on line 1802, which isn't that helpful.
Since the Vue.js script is in a separate file, I can blackbox that script from the Call Stack
pane in order to make this
click breakpoint more useful.
The next time I click the button and trigger the
click breakpoint, it executes the Vue.js
code without pausing in it, and then pauses on the first line of code in my app's listener,
which is where I really wanted to pause all along.
A request from the DevTools team: consider Canary
If you're on Mac or Windows, please consider using Chrome Canary as your default development browser. If you report a bug or a change that you don't like while it's still in Canary, the DevTools team can address your feedback significantly faster.
The best place to discuss any of the features or changes you see here is the firstname.lastname@example.org mailing list. You can also tweet us at @ChromeDevTools if you're short on time. If you're sure that you've encountered a bug in DevTools, please open an issue.
Discover other DevTools features
Below is a list of everything that's been covered in the What's New In DevTools series.
- Visualize performance metrics in the Performance panel.
- Highlight text nodes in the DOM Tree.
- Copy the JS path to a DOM node.
- Audits panel updates, including a new audit that detects JS libraries and new keywords for accessing the Audits panel from the Command Menu.
- Hover over a Live Expression result to highlight a DOM node.
- Store DOM nodes as global variables.
- Initiator and priority information now in HAR imports and exports.
- Access the Command Menu from the Main Menu.
- Picture-in-Picture breakpoints.
- Live Expressions in the Console.
- Highlight DOM nodes during Eager Evaluation.
- Performance panel optimizations.
- More reliable debugging.
- Enable network throttling from the Command Menu.
- Autocomplete Conditional Breakpoints.
- Break on AudioContext events.
- Debug Node.js apps with ndb.
- (Bonus Tip) Measure real world user interactions with the User Timing API.
- Eager Evaluation.
- Argument hints.
- Function autocompletion.
- ES2017 keywords.
- Lighthouse 3.0 in the Audits panel.
- BigInt support.
- Adding property paths to the Watch pane.
- "Show timestamps" moved to Settings.
- Search across all network headers.
- CSS variable value previews.
- Copy as fetch.
- New audits, desktop configuration options, and viewing traces.
- Stop infinite loops.
- User Timing in the Performance tabs.
- Network tab renamed to Page tab.
- Dark theme updates.
- Certificate transparency information in the Security panel.
- Site isolation features in the Performance panel.
- Blackboxing in the Network panel.
- Auto-adjust zooming in Device Mode.
- Pretty-printing in the Preview and Response tabs.
- Previewing HTML content in the Preview tab.
- Local Overrides support for styles inside of HTML.
- (Bonus Tip) Blackbox framework scripts to make Event Listener Breakpoints more useful.
- Local Overrides.
- New accessibility tools.
- The Changes tab.
- New SEO and performance audits.
- Multiple recordings in the Performance panel.
- Reliable code stepping with workers in async code.
- Multi-client remote debugging support.
- Workspaces 2.0.
- 4 new audits.
- Simulate push notifications with custom data.
- Trigger background sync events with custom tags.
- Top-level await in the Console.
- New screenshot workflows.
- CSS Grid highlighting.
- A new Console API for querying objects.
- New Console filters.
- HAR imports in the Network panel.
- Previewable cache resources.
- More predictable cache debugging.
- Block-level code coverage.
- Mobile device throttling simulation.
- View storage usage.
- View when a service worker cached responses.
- Enable the FPS meter from the Command Menu.
- Set mousewheel behavior to zoom or scroll.
- Debugging support for ES6 modules.
- New Audits panel.
- 3rd-Party Badges.
- A new gesture for Continue To Here.
- Step into async.
- More informative object previews in the Console.
- More informative context selection in the Console.
- Real-time updates in the Coverage tab.
- Simpler network throttling options.
- Async stacks on by default.