Input Lag Guide
Understanding display input lag and how to measure it accurately
📚 What is Input Lag?
Input lag is the time delay between a signal being sent to your display (e.g., pressing a button) and the actual pixel change appearing on screen. It's measured in milliseconds (ms).
⏱️ Input Lag Timeline
Display input lag = Time from signal input → visible pixel change on screen
❌ Why Browsers Can't Measure Input Lag
Browser-based tests cannot measure true display input lag because:
- JavaScript cannot detect when pixels actually change on your physical display
- OS and GPU introduce frame buffering delays that are hidden from browsers
- Display panels have internal processing that adds unmeasurable latency
What browser tests actually measure:
⚠️ You cannot separate display lag from the total without specialized hardware
🔬 How to Measure Input Lag Accurately
🎯 Leo Bodnar Input Lag Tester
The most popular consumer-grade tool ($200-300). Generates a signal and measures the exact time until the display shows the change.
📹 High-Speed Camera Method
Record both a CRT monitor (0ms reference) and your test display showing the same frame. Count the frame difference at 240-1000fps.
📊 Professional Review Sites
Sites like RTINGS, TFTCentral, and Hardware Unboxed test monitors with professional equipment and publish input lag measurements.
📊 Typical Input Lag Values
💡 Note: For competitive gaming (CS:GO, Valorant, fighting games), aim for under 10ms total input lag. Casual gaming is fine with 15-20ms.
⚡ How to Reduce Input Lag
🖥️ Display Settings
- ✓ Enable Game Mode / Low Latency Mode
- ✓ Disable image processing (Dynamic Contrast, Super Resolution)
- ✓ Disable Motion Smoothing / Frame Interpolation
- ✓ Use native resolution (no scaling)
💻 Software Settings
- ✓ Disable V-Sync (adds 16-50ms lag)
- ✓ Use G-Sync / FreeSync instead
- ✓ Enable NVIDIA Reflex / AMD Anti-Lag
- ✓ Cap FPS slightly below refresh rate
🎮 Hardware
- ✓ Use wired mouse/keyboard (1-2ms vs 5-10ms wireless)
- ✓ High polling rate mouse (1000Hz)
- ✓ Use DisplayPort 1.4 or HDMI 2.1
- ✓ Upgrade to 240Hz+ gaming monitor
❌ What Adds Lag
- ✗ V-Sync enabled: +16-50ms
- ✗ Motion smoothing: +20-50ms
- ✗ Wireless mouse: +4-8ms
- ✗ Image processing: +10-30ms