QUICify

QUICify

A modern network transport for Minecraft, built on QUIC. It replaces the game's plain TCP connection with an encrypted, multiplexed, zstd-compressed one, so chunk loading stops holding up your chat, your movement and your keepalives.

Unlike other networking mods, QUICify needs no special address, no manual prefix and no port juggling: a server running it simply advertises QUIC in its status ping, and a client running it picks that up and connects over QUIC on its own. If anything at all goes wrong, the connection quietly falls back to vanilla TCP. Vanilla clients and vanilla servers never see a difference.

Please share with us your experience with this mod on our Discord!

What it actually does

• QUIC instead of TCP: One UDP connection, standard QUIC (quiche, via Netty's QUIC codec), with TLS 1.3 and ALPN. Head-of-line blocking, the 3-way handshake and TCP's loss recovery all go away.
• Stream multiplexing: Packets are spread over five QUIC streams by category; control, real-time, UI, ambient and world data, each with its own send priority. A multi-megabyte chunk burst no longer sits in front of a chat message or a movement packet.
• zstd compression with a warm context: Vanilla compresses every packet from scratch with zlib, which is the worst case for a compressor. QUICify keeps one zstd context alive per stream, so everything already sent acts as a dictionary for what comes next. On near-identical successive packets, the internal test measures 4109 bytes down to 14.
• Encrypted by default: The whole connection lives inside TLS 1.3. The login handshake binds to the server's TLS certificate instead of vanilla's cleartext RSA key exchange, which is what makes an active man-in-the-middle fail rather than merely inconvenient.
• BBR congestion control: Minecraft's traffic is a huge burst right after login, then small latency-sensitive packets at 20 Hz; a pattern loss-driven back-off handles poorly. BBR is the default, CUBIC (vanilla) stays selectable.
• Visible from F3: The debug screen gets its own block: QUIC status, multiplexing state, live rtt / congestion window / loss, and packets per second for each category.

Installation

Install QUICify on both the server and the client. The server is what advertises QUIC, the client is what acts on the announcement. Either side alone changes nothing: the connection stays on vanilla TCP.

Nothing needs configuring. The server binds its QUIC listener on the same port number as its TCP one (UDP instead of TCP), so in most cases the only thing to do is open that port for UDP in your firewall. Everything else has a working default.

Settings live in Options → Online → QUICify, or through Mod Menu if you have it: connection mode (auto / force TCP / force QUIC), UDP port, multiplexing, compression level and window, congestion control, handshake timeout.

Requirements

• Fabric Loader and Java 25
• Fzzy Config (the config screen)

The QUIC and zstd native libraries are bundled for Windows, Linux and macOS. On any other platform the mod loads, detects it cannot start QUIC, and does nothing at all: the game runs on vanilla TCP exactly as before.

Real-world results depend on your connection! QUIC helps most where TCP hurts most: packet loss, mobile and satellite links, long round trips. On a clean local network, expect the multiplexing and the compression to carry the improvement rather than the transport itself.

Links & support

• Source code: github.com/ZapMC-Mods/QUICify
• Bug reports: the issue tracker
• Discord: discord.gg/MursZT2zJ4

Licensed under MIT.