How to Turn Off Auto-Brightness on Your iPhone

The Problem with Automatic Brightness

Every modern iPhone is equipped with an ambient light sensor hidden in the notch or Dynamic Island at the top of the screen. This sensor constantly monitors the light levels in your physical environment and automatically adjusts your screen’s brightness to match.

If you walk outside into direct sunlight, the screen automatically cranks to maximum brightness so you can see it. If you walk into a dark bedroom, the screen instantly dims so it does not blind you. Apple leaves this feature turned on by default because it is arguably the single most effective way to preserve your iPhone’s battery life.

However, the auto-brightness algorithm is not perfect. Sometimes it aggressively dims the screen when you are just trying to watch a movie in a slightly shadowed room. Other times, the constant flickering back and forth between brightness levels as you walk through a house can trigger headaches or eye strain. If you want to take manual control of your screen, you need to turn this feature off.

But Apple does not make it easy to find.

Why Is It So Hard to Find?

Logically, if you want to change a screen setting, you would open the Settings app and go to “Display & Brightness.” You will find a brightness slider there, along with toggles for Dark Mode, True Tone, and Night Shift.

However, you will not find the Auto-Brightness toggle on that page.

Because Apple strongly prefers that you leave this battery-saving feature enabled, they have intentionally buried the toggle deep inside the Accessibility menus, hoping most users will never bother looking for it.

How to Turn Off Auto-Brightness on iOS

These steps apply to all modern iPhones running iOS 14, iOS 15, iOS 16, and iOS 17.

1. Open the Settings app on your iPhone.
2. Scroll down past the “Display & Brightness” section. Do not click it.
3. Instead, look for the section labeled Accessibility (it has a blue icon with a white figure inside a circle). Tap on it.
4. Under the “Vision” heading at the top of the screen, tap on Display & Text Size.
5. You are now in the correct menu, but you still have to scroll all the way down to the very bottom of the page.
6. The very last option on the list is Auto-Brightness.
7. Tap the green toggle switch to turn it Off (the switch will turn grey).

Apple includes a small warning note below the toggle stating, “Turning off auto-brightness may affect battery life and long-term display performance.” This is technically true (leaving an OLED screen at maximum brightness for hours on end will drain the battery rapidly and could theoretically cause screen burn-in), but as long as you manually manage the brightness, you have nothing to worry about.

How to Manually Adjust Your Brightness

Now that the ambient light sensor is disabled, your screen will remain at the exact brightness level you set it to, regardless of whether you are in a dark closet or on a sunny beach.

To manually change the brightness quickly:

1. Swipe down from the top-right corner of your screen to open the Control Centre. (If you have an older iPhone with a physical Home button, swipe up from the bottom edge of the screen).
2. Look for the tall vertical slider with the Sun icon inside it.
3. Tap and drag the slider up to increase the brightness, or drag it down to dim the screen.

Your iPhone will now permanently lock the screen at that specific intensity until you manually drag the slider again.

What is True Tone, and Should I Turn it Off Too?

When you take manual control of your screen, you might notice that the colours still look slightly “warm” or yellow in certain rooms, and “cool” or blue in others.

This is not Auto-Brightness; this is a separate feature called True Tone. While Auto-Brightness changes the intensity of the light, True Tone uses advanced sensors to change the colour temperature of the screen to match the ambient lighting in your room, making the screen look more like a natural piece of paper.

If you are a photographer or graphic designer who needs 100% colour accuracy, you should turn this off as well.

1. Go to Settings > Display & Brightness (True Tone is actually located in the logical place).
2. Look for the True Tone toggle just below the Brightness slider.
3. Tap the green switch to turn it Off.

With both Auto-Brightness and True Tone disabled, you now have complete, absolute manual control over your iPhone’s display.