inputlag-tester

Small Windows utility to measure input → DXGI capture latency of a game or application.

⚠️ Important: this program measures the time between a mouse movement and DXGI detecting a frame change on Windows.
It does not directly measure the actual display output time (scan-out + panel response).

also very important, this tool may not/doesn't work:

• if you are performing a screen cloning, it works when expanding screen
• or with exclusive fullscreen mode, need to be borderless/windowed mode.

Features

• Automatically detects monitor refresh rate (Hz) via DXGI
• Reports latency in milliseconds and in number of frames
• Statistics: min, median, average, p95, p99, max, standard deviation
• Configurable parameters (sample count, interval, capture region, etc.)

Local build (MSVC)

Requirements: Visual Studio with C++ toolset (MSVC) or Visual Studio Build Tools.

cl /std:c++17 inputlag-tester.cpp /link dxgi.lib d3d11.lib kernel32.lib user32.lib

L'exécutable inputlag-tester.exe sera généré dans le répertoire courant.

Usage

1. Launch your game and go to the firing range for example

2. Launch an Command prompt or Powershell window

3. drag-n-drop the .exe binary into the Command prompt window with additional options if needed

   inputlag-tester.exe -n 100 -interval 200 -warmup 10

4. Go back to the game in less than 3 seconds

Options

• -n : total number of samples (default: 210)
• -warmup : number of initial samples to ignore (default: 10)
• -interval : delay between mouse moves in milliseconds (default: 50)
• -x <X> -y <Y> : top left corner of the capture region (0,0 = top left corner of the screen)
  • default: X=((screenWidth / 2) - (width / 2)) et Y=((screenHeight / 2) - (height / 2))
• -w <width> -h <height> : capture region box size (default: 200x200 centered square)
• -dx : horizontal mouse movement amplitude (default: 30)

How to interpret results

• What is measured:
  mouse movement -> frame change observed by DXGI
• Includes: game engine, GPU, Windows compositor, DXGI desktop duplication.
• Does not include: display scan-out time, panel response time.

For true input-to-photon measurements (up to the light emitted by the display), you need a high‑speed camera or a photodiode attached to the screen.

Releases

Pre-built Windows binaries are automatically published in the Releases tab whenever a vX.Y.Z tag is pushed.

Output example

Here an example for expected output (output from my computer, below my computer specs)

• AMD Ryzen 7 7700x 8-core
• Nvidia GeForce RTX 4080
• écran ROG PG27AQN (IPS 360Hz screen) en DisplayPort
• Windows 11 25H2

PS C:\Users\Vigne> PS Z:\sv\CODE\inputlag-tester> .\inputlag-tester.exe -interval 1ms -o results.txt

========================================
   inputlag-tester (Auto-Detect Hz)
========================================

Config: dx=30 interval=50ms n=210 warmup=10

[DXGI] OK Screen resolution: 2560 x 1440
[DXGI] OK Detected refresh rate: 360 Hz
[DXGI] OK Auto-region: x=1180 y=620 w=200 h=200 (center)
[DXGI] OK Desktop Duplication initialized
Monitor: 360Hz (2.78 ms per frame)

[OK] Starting test in 3 seconds...
[OK] Measurements starting (pure DXGI-based)...

[1/210] Latency: 0.31 ms (0.11 frames)
[2/210] Latency: 0.62 ms (0.22 frames)
[3/210] Latency: 0.39 ms (0.14 frames)
...
[209/210] Latency: 0.78 ms (0.28 frames)
[210/210] Latency: 0.83 ms (0.30 frames)

==========================================
              FINAL RESULTS
==========================================

[SYS ] CPU           : AMD Ryzen 7 7700X 8-Core Processor
[SYS ] CPU Cores     : 16 logical cores
[SYS ] RAM           : 31911 MB
[SYS ] OS            : Windows 6.2 (build 9200)
[SYS ] GPU           : NVIDIA GeForce RTX 4080
[SYS ] GPU VRAM      : 16048 MB
[SYS ] Monitor       : \\.\DISPLAY1
[SYS ] Refresh Rate  : 360 Hz

[*] Input -> DXGI Capture Latency (milliseconds)
    Samples       : 200
    Min           : 0.30 ms (0.11 frames)
    P50 (Median)  : 0.61 ms (0.22 frames)
    Avg           : 0.61 ms (0.22 frames)
    P95           : 0.79 ms (0.28 frames)
    P99           : 0.95 ms (0.34 frames)
    Max           : 1.00 ms (0.36 frames)
    Std Dev       : 0.10 ms

[*] Monitor Analysis (360Hz)
    Frame time    : 2.78 ms
    Verdict       : EXCELLENT - Under 1 frame of lag

[*] Test Characteristics
    Test Duration : 6571 ms
    Measurement Rate : 30.44 Hz
    Interval      : 1 ms

[+] Test completed successfully

Note: these measurements represent the time between a mouse movement
      and DXGI detecting a frame change on Windows.
      They do not include the exact display output time
      (scan-out + panel response), which requires a hardware sensor.

[OK ] Results written to: results.txt