The Google Pixel 4 comes with a 90Hz display, but it does not run at 90Hz all of the time, luckily you can force it to do so. This is different from how the OnePlus 7 Pro and 7T Series have done it, and it's in an effort to conserve battery life.
And in fact, we're noticing that a lot of the time, the Pixel 4 is going to stick to 60Hz instead of bumping up to 90Hz, unfortunately. But there is a fix for that.
There's a way that you can force the Pixel 4 to stay in 90Hz all of the time. But of course, that also means that the already small battery is going to take a huge hit.
How to Force 90Hz refresh rate
First things first. You're going to need to enable "Developer Options". To do this, go into Settings, scroll to the bottom of the screen and tap on "About Phone". Now scroll to the bottom of that screen and tap on the Build Number nine times. After the ninth time, it'll ask for your PIN or Passcode, if you have one on your Pixel 4.
After that, Developer Options is enabled.
Now, you'll need to go back into the main settings app and tap on System – it's just above About Phone. Now tap on Advanced, and Developer Options. It's the second to last option in this menu.
Once you're in Developer Options, you can scroll down to the "Debugging" section, it'll be the second to last option in that section.
Tap on that option.
Then Tap on the slider on the right side.
This will turn on 90 Hz all of the time.
As the screen says, this is the "highest refresh rate for improved touch responsiveness and animation quality. Increases battery usage." So enable this at your own risk. As the Pixel 4 battery is already small, and doesn't last very long, turning on 90Hz all of the time is going to make it last an even shorter amount of time.
There you have it, that's how you turn on 90 Hz Refresh Rate all the time, on the Pixel 4. It's not something that most users should be doing, as it will drain your battery a lot, and this already has a pretty small battery. But it is there for those that are brave enough, and don't mind charging multiple times a day.