The brightness slider in Settings and Control Center has no effect on iPhone 12 Pro screen brightness

It seems like the crash/restart during the Apple movie streaming might have caused some unexpected problems. However, before jumping into a full factory reset, let's try a few troubleshooting steps to see if we can resolve the problem without going to such extremes.

• Firstly, let's address the brightness issue. Start by checking the auto-brightness feature. Go to Settings > Display & Brightness and make sure the "Auto-Brightness" toggle is turned off. Sometimes, this feature can interfere with the manual brightness settings. Once it's disabled, try adjusting the brightness using the slider in the Settings or Control Center again to see if it has any effect.

• Next, let's tackle the Face ID issue. Since you mentioned that you've already updated iOS and restarted the device multiple times, it's possible that the Face ID system encountered a glitch during the crash. To troubleshoot this, go to Settings > Face ID & Passcode and try disabling Face ID. After disabling it, restart your iPhone and then re-enable Face ID. This can sometimes reset the facial recognition system and resolve any underlying issues.

• ... and as you have suspected, if these steps don't resolve the problems with brightness and Face ID, you can consider a backup and restore as a last resort. Make sure to back up your iPhone to iCloud or your computer before proceeding with the factory reset. Once the backup is complete, go to Settings > General > Reset and choose "Erase All Content and Settings." After the reset is finished, set up your iPhone as a new device or restore it from the backup you created earlier.

Note: Performing a factory reset will erase all data on your iPhone, so it's essential to have a backup to restore from.

Hopefully, one of these troubleshooting steps will help resolve the issues you're facing. If not, reaching out to Apple Support or visiting an authorized service center might be the best course of action. To contact Apple Support directly, just select the "Support" link on the lower left-hand side of this forum's web page.

My iPhones brightness doesn’t change and it took me months of just messing around with it and I accidentally kind of fixed it, it stops working every time it shuts off or dies, but all I have to do to get it to work again is change the display zoom and it’s bright again.

at first I wasn’t sure because I couldn’t get it to work at all, but when I had factory reset it the Apple logo was at full brightness but then it would go dark again, so I knew there had to be some way to get it to work, and that seemed to work for me

I saw a trick to fix this which was turning on and then back off the display zoom.

Settings > Display & Brightness > display zoom

changing other settings in display didn’t work. But for some reason. This helped my screen be visible again! Hurrah

this may be the key under accessiblity-display& text- at the very bottom there is an autobrightness toggle that comes from factory as ON It seems to override the brightness slider.

For whoever lands in this page, two other things worth checking:

• I had issues with the brightness slider not working when my phone was too hot. Leaving it away to cool down helped, and later I was able to go above 50% brightness.
• There's a setting called "Reduce White Point" which greatly mutes colors and which could be on by accident. You can find it on Settings > Accessibility > Display & Text Size > Reduce White Point.

JohanUK Said:

"Brightness slider has no effect: [...]This happened after what appeared to be the iPhone 12 Pro restarting or crashing during streaming of an Apple movie after getting the first low battery alert.[...]"

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Report this as a Bug to Apple:

Do your Part: Provide Apple with feedback on this, letting them know about this issue.  Apple may not get back to you directly, but the more feedback they receive on this, the more they will know what is occurring, and what bug fixes to include in updates to come.

1. Go Here: Feedback - iPhone - Apple
2. Select: "Bug Report" for the "Feedback Type"
3. Comment: on when this issue began, and how you have troubleshot it, thus far. Include the URL of this post
4. Proceed from there as necessary

Please check “Reduce White Point” in settings or go Accessibility-> Display & Text Size -> Reduce White Point and turn that off.

This setting reduces the intensity of bright colours.

You probably have Reduce White Point enabled. Here's how to turn it off: https://www.imobie.com/support/how-to-reduce-white-point-in-ios-10.htm

Sorry that none of that helped. Looks like your next step is to contact Apple Support directly. Good luck!

I can’t thank you enough! I’ve been having the same problem mentioned above and I tried the Display Zoom that you mentioned. It worked! Thank you!!

This is total *. I never spend my time to write reviews or complains. But this is infuriating since I've been dealing with it for years...my last update to Iphone 14 was based on hopes that this will stop and Apple steps up their game with hardware they need to take control over your settings to manage what I think is probably the heating up of components. This is insane to pay the kind of money they price their devices at just to find out you open the sunroof in your car and screen instead of staying bright with "auto-brightness" off, it goes darker...and you cant see your GPS map. (this is only one use case where this is so insane). Obviously when is on "auto-brightness" does it more often and you can only imagine how much of out of wack that is when you get more light thru sunroof and instead of brightening the screen this thing all of the sudden decides to do the opposite and you're pinch dark and cant use it. My Samsung S10 7 years old and few generations older works like a charm and manages the heat wonderfully. Screen brightness control is not the main thing if you further investigate by touching the hardware piece of the phone itself..you can tell how hot it gets and compare it with your other device (in my case the Samsung S10), both placed under same sunny warmer conditions and you can tell there is no heating of the samsung but Iphone you almost cant touch it. I am pistttttt....and have no more time to further describe....Certainly this is my last IPHONE ever.

[Edited by Moderator] 

WHAT HAPPENED TO MY IPHONE 11pro when I turn it on there is a full brightness and go down into dim suddenly and I have try to turn off the auto brightness but it also the same thing can anybody help me out I am fed up

@Makklynn

I wanted to thank you for this answer, it's what fixed my iPhone 12 mini and it drove me nuts for weeks.

It was a similar situation where the phone died while playing a video (in my case it was a TikTok one).