FreePWM Flicker Test Online — Check If Your Monitor Has Backlight Flicker
Test your monitor for PWM backlight flicker online free. Select flicker frequency, go fullscreen, and film with your phone to detect eye-strain-causing PWM dimming. No software needed.
Select a frequency, go fullscreen, then film your screen with your phone.
Check if your monitor uses PWM backlight dimming — a common cause of eye strain and headaches
Detecting your display…
A web page can only flicker up to half your display's refresh rate, so the on-screen flicker is a reference pattern. To measure your monitor's real PWM frequency, film the screen with your phone using the steps below.
15 Hz
Visual flicker rate
Preview — click Start for fullscreen
This test runs entirely in your browser. No data is collected or transmitted.
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PWM Flicker Test guide
How to use the PWM Flicker Test accurately
Test your monitor for PWM backlight flicker online free. Select flicker frequency, go fullscreen, and film with your phone to detect eye-strain-causing PWM dimming. No software needed.
01What Is PWM Dimming and Why Does It Cause Eye Strain?
PWM (Pulse Width Modulation) is a method monitors use to control brightness by rapidly switching the backlight on and off at a fixed frequency.
02How to Use This PWM Flicker Test
This tool offers two complementary checks. The Moving Line mode needs no camera: a bright bar sweeps the screen, and if your backlight uses PWM your eyes see the bar break into several separated copies instead of one smooth blur.
03PWM Symptoms: Headaches, Eye Fatigue, and Blurry Text
The sensitivity to PWM flicker varies significantly between individuals. Research suggests that people with a history of migraines, photosensitivity, or visual stress disorders are more likely to notice discomfort from PWM...
04How to Find a PWM-Free Monitor
When shopping for a PWM-free monitor, look for displays explicitly certified as "Flicker-Free" by VESA or the manufacturer.
What phone camera settings work best for the PWM flicker test?
Use your phone's standard camera app (not portrait mode). Disable auto-exposure if possible — on iPhone enable manual exposure by tapping and locking AE/AF. On Android enable Pro mode. Lower shutter speed (e.g. 1/120s) makes banding more visible.
Which test mode should I use — Flicker or Moving Line?
Use Moving Line first: it needs no camera and works at your display's native refresh rate. If the sweeping bar breaks into several separated copies instead of one smooth blur, your backlight is pulsing (PWM). Use Flicker mode when you want to film the screen with your phone to capture rolling bands.
My screen is always maximum brightness — does PWM still apply?
PWM dimming is typically only active below maximum brightness. At 100% brightness most monitors switch to continuous DC dimming. Test at 50–75% brightness for the most accurate results.
Can this tool detect PWM automatically?
The manual phone camera filming method is most reliable because it directly captures photons from the panel. Automatic webcam detection is experimental and requires a high-framerate camera (120fps+) which most laptop webcams do not have.
Is PWM harmful?
For most people, no. Sensitive individuals — particularly those prone to migraines, photosensitivity, or eye strain — may experience discomfort at PWM frequencies below 1000Hz, especially during long work sessions. Choosing a PWM-free or high-frequency (>1000Hz) monitor eliminates this risk entirely.
Windows app
KeyboardTester.click is available from Microsoft Store
Install the official Windows app shortcut, or keep using the same free testing tools in your browser.
01 / 10Phone buying guidePWM-sensitive? Test the phone, not the promiseDisplay specs narrow the shortlist, but no OLED is comfortable for everyone.02 / 10Build the shortlistStart with the display strategyCompare LCD, DC-dimming and high-frequency PWM options. Each still needs a real-use check.03 / 10Read the evidenceSpecifications are only a filterFrequency, modulation, brightness and firmware can all change how a screen behaves.04 / 10Before testingEnable the documented display settingToggle names and effects vary by model. Confirm the current manual before testing.05 / 10First passTest at your normal brightness firstUse the reading, video and scrolling tasks you actually do each day.06 / 10Low-light passRepeat at a lower brightnessOLED dimming behavior may change as brightness falls. Keep the same room and screen content.07 / 10Store checkCompare camera bands, not just one photoUse the same camera, exposure and distance on each phone for a fair comparison.08 / 10Read cautiouslyBanding is a clue, not a lab resultCamera bands can reveal pulsing, but not exact PWM, modulation or medical conclusions.09 / 10Final decisionLet the return window settle the choiceTry normal use briefly. Stop if discomfort occurs; return it before the seller's deadline.10 / 10One last checkRun one controlled flicker comparisonUse the same brightness and camera setup, then save the result with your buying notes.
01 / 10Screen flicker testYour screen may be flickeringMany displays dim by switching the backlight on and off hundreds of times a second.02 / 10The symptomSore eyes and evening headachesStrain that gets worse at night, on one device but not another, is the clue.03 / 10What PWM meansDimming by blinking, not fadingInstead of lowering brightness, the backlight pulses. Faster pulsing is easier to tolerate.04 / 10Why night is worseLower brightness, deeper flickerThe dimmer you set the screen, the longer the backlight stays off between pulses.05 / 10Run the testWatch the moving patternA flickering backlight breaks the motion into separate copies instead of a smooth trail.06 / 10What to look forBands mean pulsingClear repeated edges suggest PWM. A smooth blur suggests steady, flicker-free dimming.07 / 10Not everyoneSome people never noticeSensitivity varies widely. Migraine and dry eyes can make the same screen unbearable.08 / 10What helpsRaise brightness, lower contrastHigher brightness usually shortens the off phase. Warm light and screen breaks help too.09 / 10One honest limitA browser cannot measure hertzThis shows whether flicker is visible to you, not the exact PWM frequency.10 / 10Your turnSee how your screen dimsRun the pattern at full and low brightness, then compare your devices.
01 / 10Monitor reality check1000Hz Is Real. Worth $999?LG's UltraGear 25G590B is the first native 1000Hz 1080p monitor. Check the fine print first.02 / 10The price$999.99 for 1080pThat is the LG.com launch price, confirmed Sept 10. A 24.5-inch IPS esports panel.03 / 10The 1 ms mathOne Frame Lasts 1 msAt 1000 Hz a frame is on screen for 1 ms—the same figure as LG's own 1 ms GtG response spec.04 / 10LG's own footnoteMBR Pro Turns Off VRRFreeSync Premium and G-SYNC Compatible are disabled while MBR Pro runs. The 1100Hz overclock drops FreeSync.05 / 10Feeding itCan Your PC Push 1000 fps?LG lists Windows 11, RTX 50 / RX 9070-class GPUs and DisplayPort 2.1. 1000 Hz does not promise 1000 fps.06 / 10Reality check1080p Is Still the Majority50.52% of Steam players ran 1080p in August 2026. LG is selling speed to the biggest resolution group.07 / 10Same moneyWhat $999 Buys InsteadA 480Hz QHD OLED tracked at $547.54 on Jul 30. LG's own 480Hz dual-mode 27G850A: about $699.99.08 / 10Verdict splitBuilt for One Kind of PlayerSerious FPS competitors with GPUs to match may justify it. Everyone else buys sharper pixels for less.09 / 10Delivery dayTest Before You TrustVerify the refresh rate your system actually reports, frame skipping, dead pixels and motion clarity.10 / 10Your turnCheck Your Refresh RateSee what your browser reports right now. A browser check reads reported rate, not certified panel speed.
01 / 10Monitor checkDark scenes losing detail?Your monitor may be turning several near-black shades into one flat black.02 / 10The symptomShadow texture disappearsHair, clothing, caves and night scenes merge into featureless black. That is black crush.03 / 10Before you testUse normal SDR settingsDim the room, avoid glare and let your eyes adapt for 30 to 60 seconds.04 / 10The testLook for 32 near-black stepsPatch 1 is darkest. Patch 32 is easiest. Use fullscreen and do not expect the low steps to glow.05 / 10Read the resultFind the first visible patchIt should be barely separate from the black background. Note its number.06 / 10ExcellentYou can see 1 through 32Your display is preserving very dark shadow steps. Subtle is correct.07 / 10Mild crushingVisibility starts near 4Brightness may be too low, or gamma may be hiding the first few steps.08 / 10Moderate to severeVisibility starts at 8 or 16Check the monitor black-level setting and whether the GPU is sending Full or Limited RGB.09 / 10Fix one variable at a timeBrightness. Range. Gamma.Retest after each change. Establish a clean SDR result before troubleshooting HDR.10 / 10See what your display keepsRun all 32 shadow stepsThe live tool is the proper diagnostic surface; compressed story images are only a guide.
