Why a ProMotion iPhone reads 60 Hz here
The browser on an iPhone or iPad draws a web page at most as often as WebKit, the engine behind Safari, allows. WebKit has a setting called Prefer Page Rendering Updates near 60fps, described as preferring updates “near 60 frames per second rather than using the display’s refresh rate”, and it is on by default. So on a 120 Hz iPhone 16 Pro, this test normally shows 60 Hz. That isn’t a fault of the screen: apps and the rest of iOS still use ProMotion. The verdict above spots this and lists the switches to check in order.
Unlock 120 Hz for web pages
- Open Settings, tap Apps, then Safari.
- Scroll to the bottom, tap Advanced, then Feature Flags.
- Turn off Prefer Page Rendering Updates near 60fps.
- Quit Safari completely from the app switcher, open it again and reload this page.
The reading should now settle on 120 Hz with a frame time of 8.33 ms, and the verdict turns to Pass. The flag is for web developers: it makes every animated page draw twice as often, which costs battery, so switch it back on when you’re done testing if you prefer.
Other things that hold ProMotion at 60 Hz
- Low Power Mode or heat. Apple’s developer guide says iOS disables the faster refresh rates in low power mode or when the device gets hot.
- Limit Frame Rate. Settings, Accessibility, Motion has a Limit Frame Rate switch that caps ProMotion displays at 60 frames per second.
- Your model. Only ProMotion models reach 120 Hz: the iPhone 13 Pro and later Pro models, the iPhone 17, iPhone Air and iPhone Duo, and the iPad Pro. The iPhone 17e, iPad Air and iPad mini top out at 60 Hz.
Reading the result on a phone
ProMotion changes the rate from moment to moment, up to 120 Hz and, according to Apple, down to 10 Hz on the iPhone 13 Pro and 24 Hz on iPad Pro, and lower on later iPhones with an Always-On display. iOS decides what to use. The number here is the rate the browser is allowed to draw at while the page animates, so a steady 120 means web pages get the full rate. In the motion test, the top row moves in steps half as long as the 60 fps row.
On Android, use the Android refresh rate test. For a Mac or PC monitor there are the 144 Hz test and 240 Hz test, and any screen works with the plain refresh rate test.