How to Enable Dim Flashing Lights and Reduce Motion on iPhone to Protect Photosensitive Vision

Certain videos, films, and animations contain rapid flashing or strobing light sequences that can cause discomfort, eye strain, or even trigger photosensitive conditions such as photosensitive epilepsy. Apple has built accessibility features directly into iOS that automatically detect and dim these flashing light sequences before they reach your eyes.

This guide explains how to enable Dim Flashing Lights on your iPhone, how it works alongside the broader Reduce Motion accessibility setting, and how to configure both features for maximum comfort and visual safety.

What Does Dim Flashing Lights Do on iPhone?

The Dim Flashing Lights feature, introduced in iOS 17, uses real-time video analysis to detect sequences of rapid brightness changes in media content. When it identifies a flashing sequence that exceeds a certain intensity threshold, it automatically reduces the brightness of those specific frames, softening the visual impact without altering the rest of the video.

This feature works across multiple apps, including:

• Apple TV app — films and television programmes.
• Safari — web-based video content.
• Third-party apps — any app using the system video player framework.

It is important to understand that Dim Flashing Lights does not remove flashing content entirely. Instead, it lowers the contrast of the affected frames so the flashing is significantly less intense. The audio and overall viewing experience remain unchanged.

How to Enable Dim Flashing Lights on iPhone

Follow these steps to activate the Dim Flashing Lights feature:

1. Open the Settings app on your iPhone.
2. Scroll down and tap Accessibility.
3. Under the Vision section, tap Motion.
4. Toggle on Dim Flashing Lights.

The setting takes effect immediately. You do not need to restart your iPhone or close any apps. The next time you play a video containing rapid flashing, iOS will automatically dim the affected frames.

Understanding the Reduce Motion Setting

The Reduce Motion setting is a separate but complementary accessibility feature found on the same settings screen. While Dim Flashing Lights targets video content, Reduce Motion affects the animations and transitions throughout the entire iOS interface.

When Reduce Motion is enabled:

• Parallax effects on the Home Screen are disabled — app icons and wallpapers no longer shift when you tilt your device.
• App launch and close animations are replaced with simple cross-dissolve transitions instead of the default zoom effects.
• Animated weather effects in the Weather app are reduced or disabled.
• Message effects in iMessage (such as Slam, Loud, and Invisible Ink) play as a static preview rather than a full animation.
• Auto-playing video previews in the App Store and other Apple apps are paused.

How to Enable Reduce Motion

1. Open the Settings app.
2. Tap Accessibility.
3. Tap Motion.
4. Toggle on Reduce Motion.

Once enabled, additional sub-options appear:

• Auto-Play Message Effects — when turned off, iMessage bubble and full-screen effects require a manual tap to play.
• Auto-Play Video Previews — when turned off, video previews in the App Store, Apple TV, and other apps do not play automatically.

Using Dim Flashing Lights and Reduce Motion Together

These two features address different aspects of visual sensitivity, and enabling both provides the most comprehensive protection:

• Dim Flashing Lights handles rapid strobing in video playback.
• Reduce Motion handles animated transitions, parallax effects, and auto-playing content throughout the operating system.

You can enable one without the other, or activate both simultaneously. They operate independently and do not conflict with each other.

Adding Dim Flashing Lights to Control Centre for Quick Access

If you prefer to toggle Dim Flashing Lights on and off quickly without navigating through Settings each time, you can add an Accessibility Shortcut:

1. Open Settings > Accessibility.
2. Scroll to the bottom and tap Accessibility Shortcut.
3. Select Dim Flashing Lights from the list.

Now, you can activate or deactivate Dim Flashing Lights by triple-clicking the Side button (or the Home button on older iPhones). If you have multiple accessibility features assigned to the shortcut, a menu appears letting you choose which one to toggle.

How iOS Detects Flashing Content

Apple’s implementation uses a frame-by-frame luminance analysis algorithm that runs in real time during video playback. The system measures the rate and magnitude of brightness transitions between consecutive frames. When the analysis detects a sequence where:

• The brightness changes exceed a defined contrast threshold, and
• The changes occur at a frequency known to be potentially harmful (typically above three flashes per second)

the system intervenes by reducing the brightness differential of the offending frames. This approach is based on established photosensitive epilepsy guidelines, including the Harding Flash and Pattern Analyser standards used in broadcast television.

The processing happens locally on your device. No video data is sent to Apple’s servers, and the feature works entirely offline.

Which Devices Support Dim Flashing Lights?

Dim Flashing Lights requires iOS 17 or later. Any iPhone model capable of running iOS 17 supports the feature, including:

• iPhone SE (2nd generation and later)
• iPhone XR and later
• All iPhone 11, 12, 13, 14, 15, 16, and 17 series models

The feature is also available on iPad (iPadOS 17+), Mac (macOS Sonoma+), and Apple TV (tvOS 17+), using the same Settings > Accessibility > Motion pathway on each platform.

Limitations and Considerations

While Dim Flashing Lights is a significant step forward for accessibility, there are some limitations to be aware of:

• Not all apps are covered — apps that use custom video rendering engines rather than Apple’s system video player may bypass the dimming detection. Games with their own rendering pipelines are a common example.
• Live content — the feature works on both recorded and live-streamed video, but the real-time analysis introduces a minimal processing overhead. On older devices, this may be noticeable in very demanding playback scenarios.
• Static flashing elements — the feature targets video playback. Flashing elements in web pages created using CSS animations or JavaScript are not dimmed by this feature. For those, Reduce Motion and the browser’s prefers-reduced-motion CSS media query provide some protection.
• User interface animations — system-level animations (such as notification banners, keyboard animations, and app transitions) are handled by Reduce Motion, not Dim Flashing Lights.

Additional Accessibility Features for Visual Comfort

iOS offers several other settings that complement Dim Flashing Lights and Reduce Motion for users with visual sensitivities:

• Reduce Transparency (Settings > Accessibility > Display & Text Size) — replaces translucent backgrounds with solid colours, reducing visual complexity.
• Increase Contrast (Settings > Accessibility > Display & Text Size) — enhances the contrast between foreground and background elements throughout the interface.
• Reduce White Point (Settings > Accessibility > Display & Text Size) — reduces the intensity of bright colours on the display, which is particularly useful in dark environments.
• Night Shift (Settings > Display & Brightness) — shifts the display’s colour temperature towards the warmer end of the spectrum during evening hours.
• Dark Mode (Settings > Display & Brightness) — switches the entire interface to a dark colour scheme, reducing overall screen brightness.

By combining Dim Flashing Lights and Reduce Motion with these additional display settings, you can create a highly customised visual environment that prioritises comfort and safety while maintaining full access to your iPhone’s features and content.