Frame Skip Test — Catch Dropped Frames With Your Phone
Vertical colour bars scroll down your screen at a known speed. Record them with your phone's camera at 1/30 second shutter and any skipped frame shows up as a missing or doubled bar in the photo. The most reliable way to verify your monitor is actually displaying every frame.
How to use this test:
- Set your phone camera shutter to roughly 1/30 second.
- Record the screen while the bars are scrolling.
- Pause the recording — if any colour bar is missing or doubled, your monitor dropped a frame.
- A perfectly stable 60 Hz monitor will show even, evenly-spaced bars.
How to detect skipped frames with a phone camera
Monitors do not always display every frame the GPU sends. Sometimes the panel is busy, sometimes the cable bandwidth is insufficient, sometimes the GPU driver is buggy. The skipped frame is invisible to the eye — it just feels like a brief stutter — but it is trivial to detect with a phone camera. The trick is to match your shutter speed to a multiple of the refresh rate, so each photo captures a known number of refreshes. Any deviation from that pattern reveals a skipped frame.
On a 60 Hz monitor, a 1/30 second shutter captures exactly two refreshes. If both refreshes are displayed, your photo shows two evenly-spaced colour bars. If one refresh is skipped, the photo shows only one bar — and the bar that is shown is wider, because it was held on screen for two cycles. On a 144 Hz monitor, use 1/72 second shutter for the same effect.
Common causes of frame skipping
- Cable bandwidth. The most common cause. A 4K 144 Hz signal needs DisplayPort 1.4 (DSC) or HDMI 2.1. Using an older cable forces the monitor to skip frames to fit the available bandwidth.
- Overclocked refresh rate. Many monitors allow a slight overclock (e.g. 144 Hz → 165 Hz). At the overclocked rate, the panel cannot keep up and skips frames. Drop back to the native rate and re-test.
- Driver bugs. GPU driver updates occasionally introduce frame pacing issues. Roll back to a previous driver version to test.
- Mixed-refresh multi-monitor setups. Running a 60 Hz and 144 Hz monitor off the same GPU can cause frame skipping on the higher-rate panel, especially on Windows with NVIDIA cards. Move the second monitor to the integrated GPU or use a second GPU.
- Browser tab throttling. Browsers throttle background tabs to 1 FPS. Keep the test tab in focus and close other tabs for an accurate reading.
What the result actually means
A small number of skipped frames per minute is normal — operating systems and browsers occasionally pause the rendering pipeline for housekeeping tasks. If you see skipped frames more than a few times per minute, or in bursts, your monitor or GPU is genuinely dropping frames. Try a different cable, drop the refresh rate by one step (e.g. 144 → 120 Hz), or update your GPU driver.
Frequently asked questions
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