Update 1 (05/20/2020 @ 03:00 AM ET): The dark theme for Google App is now fully rolling out. Scroll to the bottom for more information. The article as published on September 13, 2019, is preserved below.
With the first stable release of Android 10 for the Pixel devices last week, the dark theme graduated as an easily accessible feature. Even before that, while showcasing developer previews, Google rolled out individual dark theme toggles for many of its apps such as Google Keep, Files, Photos, Fit, and many more Google apps. Back in June, Google had also started rolling out a dark theme for the Google app for certain users but at that time, the theme appeared to be partially applied and limited to only a few screens of the Google app – and only to a few users. Now, reports of complete dark theme have started to surface, with the feature now rolling out to Google Assistant as well.
A couple of Reddit users report that the dark theme for the Google app is now available without an update from the Play Store. This is apparently a server-side update and may not be instantly available to all users, even if they run the latest version of the Google App.
Evident from the gesture navigation, both of them are running Android 10 on their devices. However, few comments from users still running Android 9 Pie claim that the feature is available while they can also choose the between light and dark theme or set it to change automatically with the Battery Saver.
While the region of these users is not instantly clear, a few replies suggest that the feature may be rolling out to a batch of select users in the U.S., UK, and Australia. I don't have the feature in India yet, and it's safe to presume that the worldwide roll-out would be gradual and thus, take some time. Furthermore, Google Podcasts, which is a part of the Google app does not seem to have the new dark theme yet.
We'll update this article as we learn about the availability of the dark theme on the Google app and the Google Assistant in other regions. Feel free to comment with your region if you have received it already.
Update: Dark theme for Google App now fully rolling out
The rollout for the dark theme for the Google App was rather random at the time of the first report, likely a result of batch-wise testing. But now, the dark theme is finally rolling out to all Google App users.
As mentioned, Dark mode will be available for the Google App on Android 10 and on iOS 12 and 13. The app will use your system settings by default, but you can also choose to override the same by changing the setting within the app.