What's New In DevTools (Chrome 66)
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
Note: Check what version of Chrome you're running at
chrome://version. If you're running an earlier version, these features won't exist. If you're running a later version, these features may have changed. Chrome auto-updates to a new major version about every 6 weeks.
Read on, or watch the video version of the release notes below.
Blackboxing in the Network panel #
Note: You can hide or show columns in the Network panel by right-clicking the table header.
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.
Figure 1. The Initiator column shows that all of the requests were initiated by line 2 of
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.
Figure 2. Blackboxing
Figure 3. After blackboxing
requests.js, the Initiator column now shows more helpful results
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.
Figure 4. The Preview tab pretty-printing the contents of
analytics.js by default
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.
Figure 5. Manually pretty-printing the contents of
analytics.js via the 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.
Figure 6. Previewing HTML in the Preview tab
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
Figure 7. An example of styles defined within HTML
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.
Caution: Local Overrides can track changes like this so long as the style is defined in the HTML document that was sent over the network. If you have a script that dynamically adds styles to an HTML document, Local Overrides still won't be able to detect those changes.
Bonus tip: Blackbox framework scripts to make Event Listener Breakpoints more useful #
Note: This section is not related to Chrome 66. It's just a bonus tip about an existing feature that you may find useful.
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.
Figure 8. The
click breakpoint pauses in Vue.js' wrapper code
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.
Figure 9. Blackboxing the Vue.js script from the Call Stack pane
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.
Figure 10. The
click breakpoint now pauses on the app's listener code