Lags

Lag is a delay between an input or trigger and its observable effect in a system. It is a broad concept used across computing, networking, multimedia, and physical or biological processes. While the terms latency and lag are related, latency often denotes the inherent time delay in a system, whereas lag emphasizes the observed postponement during use.

Common domains where lag is discussed include network lag, input lag, rendering or frame lag, display lag, buffering lag in streaming, and processing lag in software. Network lag results from factors such as physical distance, routing paths, congestion, packet loss, and jitter. Input lag refers to the delay between a user action and its effect on a device or interface, while rendering lag and frame lag describe delays in generating successive images. Buffering lag occurs when data is held temporarily to smooth playback, and processing lag arises from time spent computing tasks.

Causes of lag include hardware limitations, software inefficiency, queuing and scheduling overhead, buffering strategies, and network conditions. Lag is commonly quantified as latency or round-trip time (RTT) in networking, or as frame time in graphics. In control theory and related fields, lag can be modeled as a delay element in a system’s response.

Mitigation strategies vary by domain. Reducing lag may involve increasing bandwidth and reducing hops in networks, upgrading hardware, optimizing software and graphics pipelines, lowering buffering levels, or using predictive techniques to compensate for anticipated motion. In interactive applications, lag compensation and extrapolation can improve perceived responsiveness, while in control systems, lag reduction often relies on design adjustments to the feedback loop. Understanding lag involves identifying whether delays are intrinsic or avoidable and selecting appropriate remedies to restore responsiveness.