What is the difference between input lag and ping?

Both are delays, but they occur in completely different places, and confusing them means trying to fix the wrong problem.

Ping (network latency) is the round-trip time for data between your machine and the game server, measured in milliseconds. It only exists in online play. It determines how long it takes for your action to be registered by the server and for the server's view of the world to reach you. High ping produces the characteristic symptoms of online play: opponents teleporting, being shot after you thought you had reached cover, and hits that do not register.

Input lag (end-to-end latency) is the delay between physically pressing a button and seeing the result on screen. It exists offline too, and it is the sum of a whole chain: the input device polling rate, USB transfer, the game engine processing the input, the GPU rendering the frame, the frame sitting in a buffer, transmission to the display, and finally the display's own processing and pixel response time.

Why the distinction matters practically:

A low ping does not save you from a laggy display. Many televisions add 50–100ms of processing latency unless game mode is enabled, which bypasses most image processing. This single setting is often the largest available improvement and costs nothing.

Conversely, a fast monitor and high frame rate do nothing about a distant server.

What reduces ping: a wired connection instead of Wi-Fi, choosing a nearer server region, and stopping other devices saturating the connection. Your physical distance to the server sets a hard floor no equipment can beat.

What reduces input lag: display game mode, higher frame rate, a high refresh rate display, disabling V-Sync or using a low-latency alternative, and driver-level latency reduction features.

Jitter — variation in ping — is often worse than consistently high ping.