netcode.io
netcode.io is an open-source client/server protocol for real-time multiplayer games, using UDP to exchange unreliable, unordered packets.
What netcode.io is
netcode.io is an open-source client/server protocol for real-time multiplayer games, using UDP to exchange unreliable, unordered packets. It offers a minimal connection-oriented layer without TCP head-of-line blocking. A game backend can issue connect tokens to authorize clients, and servers place them into configured slots, refusing connections when all slots are occupied. The protocol supports clean disconnects from either side and uses timeouts to identify hard disconnects. Packets are encrypted and signed with libsodium, with protections described for crafted packets, replay attacks and amplification attacks. It supports IPv4 and IPv6, plus packet tagging intended to reduce Wi-Fi jitter. Implementations are listed for C, C#, Go, Rust, Unity, Unreal Engine 4 and TypeScript. Matchmaking is not included. The project is BSD 3-Clause licensed, with no paid plans or usage limits stated. Its maker says it builds with CMake on Windows, macOS and Linux; the default build uses a vendored libsodium subset and requires CMake 3.16 or later. The documented connection flow has a client request a connect token from a REST API on the game backend.
Good
- Exchanges UDP packets without TCP head-of-line blocking.
- Connect tokens let a backend authorize clients.
- Encrypts and signs packets using libsodium.
- Supports IPv4 and IPv6 connections.
- Implementations are listed for several languages and engines.
Watch out
- Matchmaking is not included.
- Build setup requires CMake 3.16 or later.
- The documented connection flow relies on a game backend REST API.
Who it suits
It suits game developers implementing client-server networking for real-time multiplayer games who need token-authorized connections and UDP packet exchange. It does not provide matchmaking, so teams needing that function would need to account for it separately.
Verdict
netcode.io provides a focused UDP protocol for authorized client-server game connections, with packet security and multiple listed implementations. It leaves matchmaking outside its scope, and building it requires CMake 3.16 or later.
Plans and prices
From netcode.io's own pricing page, checked 9 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| netcode | Free | BSD 3-Clause licensed library · no paid plans or usage limits stated |
The facts
Each one read from netcode.io's own pages, with the date it was checked.
What it does
- Authorized access
- Connect tokens let a game backend authorize which clients can connect to a server.checked 8 Oct 2026
- Backend integration
- The documented connection flow has a client request a connect token from a REST API on the game's backend.checked 9 Oct 2026
- Build requirements
- The C library builds with CMake 3.16 or later on Windows, macOS, and Linux, and includes a vendored libsodium subset.checked 9 Oct 2026
- Client authorization
- Connect tokens let a game backend authorize which clients may connect to a server.checked 9 Oct 2026
- Client slots
- Servers assign clients to slots and deny connections when all slots are occupied.checked 8 Oct 2026
- Connection model
- It provides a minimal connection-oriented protocol over UDP for exchanging unreliable, unordered packets.checked 8 Oct 2026
- Disconnects
- The protocol supports clean client- or server-side disconnects and timeouts for hard disconnects.checked 8 Oct 2026
- Encryption
- Packets are encrypted and signed using the libsodium cryptography library.checked 9 Oct 2026
- Implementations
- The repository provides a C implementation and links to C#, Go, Rust, Unity, Unreal Engine 4, and TypeScript implementations.checked 9 Oct 2026
- Intended users
- The maker describes the protocol for real-time multiplayer games and shows a backend issuing connect tokens after matchmaking.checked 8 Oct 2026
- Known version issue
- The project says a nonce-reuse issue affected versions 1.3.5 and earlier and was fixed in 1.4.0.checked 9 Oct 2026
- License
- The C implementation is released under the BSD 3-Clause license.checked 9 Oct 2026
- Network support
- The protocol supports IPv4 and IPv6 connections and packet tagging to reduce Wi-Fi jitter.checked 9 Oct 2026
- Packet delivery
- It lets applications exchange unreliable, unordered packets over UDP without TCP head-of-line blocking.checked 9 Oct 2026
- Packet security
- Packets are encrypted and signed, with protections against crafted packets, replay attacks, and amplification attacks; cryptography uses libsodium.checked 8 Oct 2026
- Purpose
- netcode is a secure, connection-oriented client/server protocol for multiplayer games built on UDP.checked 9 Oct 2026
- Security reporting
- Vulnerability reports can be submitted privately through GitHub or by email, and fixes are made on the latest release without backports to older release lines.checked 9 Oct 2026
- Server slots
- Servers assign connecting clients to a configured slot and deny connections when all slots are occupied.checked 9 Oct 2026
- Support
- The maintainer asks users with build questions to open a GitHub issue and says he will do his best to help.checked 9 Oct 2026
- Threat protection
- The project describes protections against crafted packets, replay attacks, and packet amplification attacks.checked 9 Oct 2026
Where it runs
- Build platforms
- The maker says netcode builds with CMake on Windows, macOS, and Linux.checked 8 Oct 2026
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