Input Lag Test with a Phone Slow-Motion Video

A tool for measuring input lag — the full delay from a button press to the first change on screen. Film your thumb on the controller and the TV in one shot with your phone's slow motion (120–240 frames per second) and upload the video: the tool finds the presses, marks the frame where the picture changed, and takes the median over every attempt. Works for PS5, Xbox, PC and any screen.

How to measure input lag

3 steps
1
Film the presses

Slow motion at 240 fps, phone held still, thumb with the button and the screen in one shot at the same height. 10–15 presses with pauses of about a second — 15–20 seconds of video.

2
Upload the video and check the boxes

The amber box is the thumb and button, the teal one is the screen. When the tool is not sure of the boxes, it asks you to tap the thumb and the screen.

3
Read the lag and compare

Median, spread and every press on its own. Save the run under its setup, film the second one — the tool compares them itself.

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Film a press and the screen in slow motion and see your lag in milliseconds

Upload a slow-motion video of your presses
Thumb on the button and the screen in one shot, 120–240 fps
MP4, WEBM, MOV, MKV, AVI, WMV, FLV, 3GP, M4V, TS, MTS, M2TS, VOB, MPG, MPEG, OGV ·

How to film the video

  1. Slow motion at 240 fps (120 works too).
  2. Phone held still, thumb with the button and the screen in the shot at the same height.
  3. 10–15 presses with pauses of about a second — 15–20 seconds of video.
  4. An action with a sharp change of picture: camera view, aim, menu.

iPhone: Share → Save to Files and pick the file from there — that sends the 240 fps original.

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Features

Finds presses and screen changes itself
Thumb travel and changes inside the screen box are read on every frame; the lag is the median of 10–20 presses, not one.
The real time of every frame
The capture rate comes from the video itself — the Android tag, the iPhone ramp, the stream clock — and when it is missing the tool asks before showing any number; otherwise the error is ×4–8.
No random numbers
A number appears only when the presses and the screen changes add up to a measurement; otherwise the tool says what is wrong: a box, the frame rate or the video itself.
Frame-by-frame review
Open any press: the thumb and the screen side by side at one scale, one-frame steps, your own marks instead of the automatic ones.
Setup comparison
TV game mode, cable or Bluetooth, 60 or 120 Hz: the tool walks you through two runs and shows the difference of medians with a 95% interval.
PDF report, image and CSV
A PDF with real text, the chart and the table of presses, a PNG card, and a CSV that spreadsheets open as columns.

FAQ

My iPhone gave a 30 fps video even though I filmed in Slo-mo. What happened?

The photo picker can hand over a lightweight copy with re-timed frames. Open the video in Photos, tap Share → Save to Files and pick the file from Files — that sends the original. If the file still has no rate tag, the tool asks how you filmed it: answer 240 or 120 fps.

What exactly is measured — the console, the TV or the controller?

The whole chain at once: controller, console, game and screen — from the moment the button bottoms out to the first change in the picture. To find one link's share, make two runs changing only that link (TV game mode, for example) and compare them in the tool.

How accurate is it, and will a regular video do?

Each mark is accurate to one frame: about 4 ms at 240 fps, about 8 ms at 120 fps; the median over 10–15 presses smooths out the spread. A regular 30 fps video is not measured: a frame lasts 33 ms and the whole lag is 1–4 frames, so the number would be random. A 60 fps video is measured, but each press can be off by up to ±17 ms — not enough to compare setups.

Why doesn't the tool show a number?

A number appears only when the presses and the screen changes add up to a plausible measurement. When they don't, the tool names the reason: the box is not on the thumb, the screen does not change after the presses, the delays are scattered in a way no display produces, or the thumb moves too fast for the chosen frame rate. You can open every press and mark the frames by hand.

Which action should I film in a game?

One that changes the picture right away and strongly: switching the camera view, aiming, opening the map. Smooth animations and fades blur the start. For a test without a game, use the console's system menu.

Why is my number higher than in TV input lag charts?

Review charts measure only the display, with a light sensor on a flashing patch. Here the number also includes the controller, the console and the game itself — a game running at 30 fps adds tens of milliseconds on its own.

Why keep the thumb and the screen at the same height in the shot?

A phone camera reads each frame line by line over a few milliseconds. If the button is at the bottom of the shot and the screen at the top, their moments in one frame differ; the tool corrects for it, portrait videos included, but the correction is tighter when they sit side by side. A TV also draws its picture top to bottom, so the tool says which part of the screen you measured.

💡 Want us to improve this tool just for you?

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Who is this tool for?
🎮 Gamers
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