Peeker’s advantage is the edge a moving player (P) gains when swinging into line of sight against a holding player (H). It exists in all server-authoritative shooters due to latency. A common claim is that peeker’s advantage depends only on the holder’s connection [1]. That is correct only if the peeker’s latency is uniform. If the peeker’s uplink differs between “peek” and “shot,” the advantage grows.
Mettler, Tang, and Chen [2] provided more detailed explanation of Peeker’s Advantage in symmetrical network conditions.
Setup
One server S, two clients:
- Holder H: uplink uₕ, downlink dₕ, round-trip time Lₕ = uₕ + dₕ.
- Peeker P: uplink while revealing Lps (“peek packet”), uplink while firing Lpa (“shot packet”).
Both have the same human reaction time R. The server resolves hits. First valid shot at the server decides the duel.
Peeker's Advantage
t1 => P swings into sight.
t2 => P’s reveal reaches S afterLps and reaches H after Lps + dₕ. H first sees P at this moment.
t3 => H reacts forR. H’s shot then travels uplink uₕ. So H’s shot arrives at server at
tH = Lps + dₕ + R + uₕ.
t4 => P sees H instantly at swing time. P reacts for R. P’s shot travels uplink Lpa. So P’s shot arrives at server at
tP = R + Lpa.
Peeker’s Advantage Formula
Define the advantage D as the time gap between H’s and P’s first shots arriving at the server:
D = tH – tP.
Case 1. Uniform Peeker Latency
If peek and shot uplinks are equal (Lps = Lpa):
D = (Lps + dₕ + R + uₕ) – (R + Lps)
= uₕ + dₕ
= Lₕ.
So with uniform latency, the advantage equals the holder’s round-trip. This is the source of the saying “only your ping matters.”
Case 2. Asymmetrical Peeker Uplink
If peeker’s uplink while revealing is higher than while firing, define the delta
Lpd = Lps – Lpa > 0.
Plugging in:
D = (uₕ + dₕ) + (Lps – Lpa)
= Lₕ + Lpd.
Result
- Uniform peeker latency: advantage = Lₕ.
- Asymmetrical uplink (Lps > Lpa): advantage = Lₕ + Lpd.
In words: the peeker gains not only the holder’s round-trip but also the extra head start equal to the difference between peek uplink and shot uplink.
Next Steps
- Empirical validation/simulation
- We examined Lps – Lpa > 0 grows peeker's advantage. Naturally Lps + Lpa > 0 shrink peeker's advantage. How about that! Maybe peeker's advantage does have a solution after all (with serious tradeoff ofc).
- People has been using network throttle to cheat for ages, maybe it's time for intelligent network throttle. Maybe they already exist.
- How to mitigate and defend against such cheat.
References
[1] M. deWet and D. Straily, “Peeking into VALORANT’s netcode,” Riot Games Technology, Jul. 28, 2020. [Online]. Available: https://technology.riotgames.com/news/peeking-valorants-netcode
[2] C. Mettler, D. Tang, and Z. Chen, A study on the effects of network latency on peeker’s advantage in FPS games, Interactive Qualifying Project Report, Worcester Polytechnic Institute, 2023. [Online]. Available: https://web.cs.wpi.edu/~claypool/iqp/fps-lag-22/final-report.pdf
Citing This
@article{chen2025peeker,
title = {Peeker’s Advantage in Asymmetrical Network Latency},
author = {Chen, Yuhao and Yang, Tianchi},
year = {2025}
}