Server-Authoritative Browser Multiplayer Game with Prediction and Lag Compensation

The problem: multiplayer feels bad on real networks

Every realtime multiplayer game has to hide latency. Players in Pakistan often connect to servers in the Gulf or Europe, so a round trip is far from instant, and mobile data adds jitter on top. Naive netcode, where the client sends input and waits for the server to reply, feels like moving through mud. Trusting the client instead makes cheating trivial. The industry answer is an authoritative server with prediction, reconciliation, interpolation and lag compensation, and it is notoriously hard to get right.

Small studios and indie developers building web or mobile multiplayer games hit this wall early, and most student multiplayer projects stop at "it works on LAN".

What already exists and the gap

• Colyseus is an open-source Node.js multiplayer framework with state synchronisation, but prediction and lag compensation are left to the developer.
• Photon (Fusion and PUN) offers hosted multiplayer with prediction for Unity, as a commercial service.
• Nakama by Heroic Labs provides an open-source game server with realtime matches and social features.
• Gabriel Gambetta's Fast-Paced Multiplayer articles and Tim Ford's GDC talk on Overwatch's gameplay architecture and netcode explain the techniques clearly.

The gap is a small, well-measured, open reference implementation for the browser that shows each technique on and off, with a network lab to prove it. Frameworks hide the hard part; articles explain it without code you can stress test.

What you build

A top-down arena shooter or racing game where the server runs a fixed tick (for example 30 Hz) and is the only source of truth. Players send timestamped input commands. The server simulates, then sends snapshots. The client predicts its own movement, reconciles on each snapshot, interpolates other players between snapshots, and renders. When a player fires, the server rewinds other players' hitboxes to the moment the shooter saw them, capped at a maximum rewind window.

Around the game you build the network lab: a proxy between clients and server that adds latency, jitter and loss, bot clients that play scripted routes, and an overlay that draws the server's view next to the client's.

The technically interesting part

The hard problem is keeping three timelines consistent: the client's predicted present, the server's authoritative present, and the interpolated past in which remote players are drawn. Your simulation step must be deterministic enough that replaying the same inputs gives the same result on client and server, or reconciliation will jitter. Lag compensation has a fairness trade-off (the shooter is rewarded, the target can be hit behind cover) and you should measure and discuss it, the same trade-off the Valve and Overwatch write-ups describe.

Show evaluators the overlay at 200 ms with prediction off, then on, and the hit registration test results.

How to evaluate it

• Correction distance: average and 95th percentile distance between predicted and authoritative position at 50, 150 and 250 ms RTT, with and without jitter.
• Hit registration: in scripted bot duels, the percentage of shots that hit on the shooter's screen and were confirmed by the server.
• Bandwidth: bytes per second per player before and after delta compression, at 16 players.
• Server cost: CPU per match and matches per small cloud instance.
• Feel: a blind test with at least 10 players rating responsiveness for different configurations.

Suggested plan

1. Weeks 1 to 4: read Gambetta's series and the GDC talk, build a local deterministic simulation.
2. Weeks 5 to 9: authoritative server, naive networking, and the network lab proxy.
3. Weeks 10 to 14: prediction and reconciliation, debug overlay, first measurements.
4. Semester 2, weeks 1 to 5: interpolation, lag compensation and hit tests.
5. Weeks 6 to 9: binary protocol, delta compression, bots and load tests.
6. Weeks 10 to 14: user test, measurement write-up, deployment and demo.

Path to a product

Realistic routes are an open-source library for browser games with paid support, or a small hosted game server product for studios making casual multiplayer and educational games. The first customer is an indie studio or a game jam team that needs working netcode for a web game. The measurement lab is valuable on its own as a testing tool for other studios.

Scope warning

Do not build accounts, progression, cosmetics or a store. Do not attempt a 3D shooter or physics-heavy vehicles; rigid body physics makes determinism much harder. One map, one weapon and one movement model with excellent netcode is the project.

Learn what you need on Sefism

• System design roadmap : latency, consistency and scaling realtime servers.
• Beej's Guide to Network Programming : sockets, TCP versus UDP and what packets really do.
• Game Programming Patterns : game loops, commands and double buffering used in netcode.
• GDC Vault : where the Overwatch netcode talk and similar postmortems live.
• Grafana k6 Documentation : load testing ideas for many concurrent connections.

Get help with this idea

Netcode projects fail when students tune by feel instead of measuring, so plan the lab early. Bring your proposal and we can agree the scope, pick a stack your team can finish with, and design an evaluation your panel will respect. You build it; we help you make the calls.

• Discuss this idea with a mentor
• Send a query to Tauseef
• Book a 1:1 session

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