What Is Input Lag?
Input lag is one of the most misunderstood metrics in competitive gaming. It's not a single number — it's the sum of every delay in the chain between your fingers and your screen. Understanding where those milliseconds hide is the first step to eliminating them.
Definition
Input lag (also called input latency or end-to-end latency) is the total elapsed time between a physical input event — pressing a key, clicking a mouse button, or moving an analog stick — and the corresponding visual change appearing on your display.
In competitive contexts, lower input lag means your game state reflects your actions sooner, giving you tighter control and a real mechanical advantage over players on higher-latency setups.
Top-tier competitive setups achieve click-to-photon latency below 10 ms. Most stock Windows configurations sit between 30–80 ms.
The Latency Chain
Input lag is not caused by a single component — it's the accumulated delay of every link in a chain that runs from your peripheral to your retina.
1 — Peripheral Polling Delay
Your mouse or keyboard reports its state to Windows at a fixed interval called the polling rate. At 1000 Hz, that's one report every 1 ms. At 125 Hz (the Windows default for many devices), it's 8 ms. This polling interval adds a worst-case delay of one full polling period.
2 — Driver & OS Processing
Windows queues hardware input events through the Human Interface Device (HID) stack. The kernel-mode driver processes raw reports, converts them to Win32 messages, and queues them for the application. Timer resolution, CPU scheduler latency, and DPC (Deferred Procedure Call) delays all contribute here.
3 — Game Engine Sampling
Games read input state at the start of each frame. If a mouse button is pressed between two frame reads, the game won't see it until the next frame. At 60 FPS, that's up to 16.67 ms of additional delay. At 240 FPS, it shrinks to 4.17 ms — which is why high framerates directly reduce perceived input lag.
4 — Render Pipeline
After the game processes input, the scene must be rendered. GPU workload, draw call overhead, and command buffer depth all add time here. Render latency varies widely depending on the game's graphics engine and your hardware.
5 — Display Processing
The finished frame travels over DisplayPort or HDMI to your monitor. Modern gaming monitors add 1–4 ms of panel processing (scaler latency). Response time (GtG) is a related but separate metric — it describes pixel transition speed, not input processing delay.
How It's Measured
Accurate end-to-end measurement requires capturing both the input event and the resulting pixel change on the same timeline. Professional methods include using a high-speed camera (1000+ fps) pointed at both the input device and the screen simultaneously.
For system-level benchmarking without specialized hardware, tools like LDAT (Latency Display Analysis Tool) or software-based click-to-photon tests can give you reproducible baselines. Our browser-based Responsiveness Lab measures the input-to-rendering side within the browser environment — useful for detecting system inconsistencies.
What Numbers Actually Matter
The difference between 5 ms and 10 ms is imperceptible to even professional players. The meaningful threshold is roughly 30 ms — above this, the lag becomes cognitively noticeable in fast-paced games. Below 20 ms, improvements are felt more as a general 'tightness' than a specific delay reduction.
Consistency matters as much as average latency. A system that delivers 15 ms 90% of the time but spikes to 60 ms unpredictably feels worse than one that holds a steady 20 ms. Frame time variance and input jitter are often more impactful than raw averages.
Display Lag vs System Lag
Display lag refers specifically to the processing delay inside your monitor's scaler and panel controller. It's independent of your PC's render pipeline and is fixed per display model.
System lag encompasses everything from peripheral polling through game engine processing and GPU rendering. This is what InputLag's optimization tools target. The two stack additively — eliminating system lag while keeping a high-lag monitor still leaves you behind.
Gaming monitors marketed as '1 ms response time' describe GtG pixel switching speed, not display input lag. These are entirely different specifications. A monitor can have 1 ms GtG and 30 ms input lag simultaneously.
Frequently Asked Questions
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