How does the server know what time the client fired the shot at?
The client includes a timestamp in every shot packet — the client's local game tick when the fire button was pressed. When the server receives that packet (delayed by network latency), the packet still carries the original timestamp. The server uses that timestamp to rewind to the corresponding world snapshot and test collision there.
Answered in
Time-Travel Fairness: How Servers Rewind for Lag CompensationWhy lag compensation rewinds the game world to when a shot was fired, and why victims experience the cost.
Read the full analysisOther questions this article answers
- Why does lag compensation exist at all? Can't players just aim for where the enemy is now?
- What happens to the player who gets shot from behind cover? Is that not unfair to them?
- How far back can the server rewind? Can it go back 500ms or 1 second?
- What happens if the ring buffer doesn't have a snapshot for the timestamp on the packet?
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