MCVoice

Proximity voice chat for Minecraft Java Edition that works without any server plugin. Voice is relayed through an MCVoice backend, never through the Minecraft server. Players who use the ordinary Simple Voice Chat mod can still be heard on servers that run the Simple Voice Chat plugin.

Stable 0.1.12 adds SVC-style controls, one microphone mode and twenty-member group policies. The public backend is updated. See controls and migration and release verification.

• Positional 3D audio (equal-power stereo panning, distance attenuation), Opus at 48 kHz in 20 ms frames, a jitter buffer and a whisper mode.
• The local entity rule. Positional voice from a speaker is played only while they currently exist as a tracked player entity in the listener's own Minecraft world, within range. This holds on proxy networks (Velocity/BungeeCord) where sub-servers share an address, dimension names and coordinates. The one exception is voice groups, which members join on purpose. See proximity security.
• Encrypted voice (AES-128-GCM with replay protection and key rotation) and Minecraft account verification through Mojang's session server. Access tokens never leave the client towards our backend.
• Hybrid Cloud + Simple Voice Chat. An independent implementation of the SVC client protocol reaches SVC-only players. MCVoice users connected both ways are heard exactly once (sender-aware deduplication), and the mod falls back to SVC when the cloud is unreachable. See SVC interop.
• Voice groups. Up to 20 players hear each other everywhere, even on different servers: search and join active groups, or create one with an optional password (Voice Chat > Groups). The menu loads 20 groups at a time and fetches more as you scroll; searching starts a fresh page of matching codes. Groups use the same push-to-talk or voice-activation mode as nearby speaking. Normal groups keep your speech inside the group while letting you hear nearby outsiders; Open groups also speak nearby; Isolated groups hear only their members. Normal is the default. These choices require an updated backend; older backends retain explicitly selected legacy Open groups.
• Two interchangeable backends, in Rust (Tokio/axum) and Go, that pass the same black-box conformance suite.
• Minecraft 1.8 → 26.3 on Forge, Fabric and Legacy Fabric (gaps listed with reasons). Every supported jar is built and validated by CI (see below).

Supported Minecraft versions

0.1.12 is published for all 62 supported Minecraft versions (102 validated jars). Both backend images and byte-verified Maven packages are published. The public Rust backend runs 0.1.12 with Normal/Open/Isolated groups and a twenty-member limit. See the release report.

The authoritative, CI-generated matrix is versions/supported.md (machine-readable: versions/versions.json + versions/build-status.json). A version and loader is listed as supported only when CI built and validated its jar. Versions not built are marked with the reason, for example no upstream loader, or not implemented yet.

Download the jar for your Minecraft version and loader from Releases. Each tag is v<version>-mc<minecraft>, and each release includes checksums-sha256.txt.

For players

1. Put the jar into mods/. Fabric needs Fabric API. Legacy Fabric needs Legacy Fabric API on the versions that have it (1.8, 1.8.9, 1.9.4, 1.10.2, 1.11.2, 1.12.2); on 1.8.1–1.8.8 the mod works without it.

2. Join any server. Nothing is needed on the server.

3. Press V for the voice menu. Select your audio devices in Settings > Audio and choose push-to-talk or voice activation in Settings > General. In Key Bindings, choose your talk key and optionally a whisper key; keyboard and mouse buttons are supported. Talk and whisper start unbound.

   • M: mute/unmute in voice-activation mode;
   • N: disable/enable voice chat (both speaking and listening);
   • H: hide/show voice icons;
   • G: groups on Minecraft 1.21.5 and earlier; unbound on 1.21.6+.

   All bindings also appear in Minecraft's Controls. Joining a group does not automatically turn on voice activation. Whisper uses the same group routing policy: it never makes a Normal/Isolated group audible to nearby outsiders.

4. The HUD shows who is talking top left, including yourself when your microphone detects voice while transmitting. Your microphone appears bottom right while push-to-talk is held or voice activation is enabled (including group open mic): grey without voice activity, green while speaking. Muting or deafening shows a red crossed icon while the indicator is visible. Open the chat and click another player's name to change their volume or mute them. The adapters preserve server name colours and prefixes in the HUD and add a green microphone beside visible speaking players' name tags. Compact, shaded pixel icons use a 10-pixel grid in speaker rows and an 8-pixel grid on name tags. The microphone indicator defaults to 16 pixels, using the same shaded artwork. Older adapters draw the same pixel artwork directly, preserving vanilla name-tag visibility and range checks. Fabric name-tag hooks are optional: if another mod prevents a hook from applying, its icon can be skipped without a required-injection startup error. Essential HUD and tick hooks stay required. These indicators are rendered by MCVoice on the listener's client. In a voice group, every member's head appears at the right edge, including quiet members. A speaking member gets a white outline and their name to the left. Unknown skins use Minecraft's default skin. Group HUD in General settings is on by default; turn it off to hide the roster.

5. Settings live in config/mcvoice.json:

   • backend URL (default: the public backend wss://mcvoice.ravoxx.dev/v1/control);
   • activation mode (push-to-talk or voice activation) and its threshold;
   • gain, devices and distances;
   • per-player volume and mute. The Players tab searches online voice users by name and keeps formatted names aligned with their controls. It lists confirmed MCVoice peers in the local world, current group members, and connected SVC users reported by the server, including quiet users;
   • HUD and debug options. Edit HUD in General settings lets you drag the speaker list and microphone, choose a vertical or horizontal list, toggle its background, and set microphone size (10–32 pixels). Done saves the layout. The group roster can be dragged independently, with its own background toggle and head size (10–32 pixels, fitted down for large groups on small screens). Cancel or Escape discards edits; Reset restores defaults in the editor. Positions follow changes in window size and GUI scale.

Audio is never recorded or stored by the mod or by the backend.

For backend operators

cd deployment/compose
cp ../../backend/rust/.env.example .env   # set secrets, PUBLIC_HOSTNAME and TRUSTED_PROXY_CIDRS
docker compose up -d                      # backend + Caddy (TLS for wss://), UDP 24455

Images: ghcr.io/ravoxx/mcvoice/voice-backend-rust and …/voice-backend-go. Kubernetes manifests, configuration, scaling and monitoring: backend deployment. Never commit a real .env.

Compose requires an explicit trusted Caddy peer or dedicated proxy-network CIDR. See proxy configuration and first startup before starting the backend; do not trust client-supplied forwarding headers.

Repository layout

Path	What
protocol/	Normative protocol v1, dedup state machine, byte-exact test vectors
backend/rust, backend/go	The two backends (Dockerfiles, .env.example)
client/	Version-independent Java 8 client core (network, audio, SVC compat, UI, proximity)
client/platform/	Minecraft adapters per API family (mojang for 1.16.1+, legacy for 1.8–1.12.2)
tools/port-version/	Generates the per-version Gradle builds, validates jars, creates mc/<version> branches
tools/versions/	Version matrix from official metadata; CI build status
tools/load-test/, tools/protocol-tests/, tools/svc-interop/	Load generator, cross-implementation tests, real SVC server probe
deployment/	Docker Compose and Kubernetes
docs/	Documentation

Branch main holds all of the above. Each mc/<version> branch is main plus the generated minecraft/ build for that version.

Building and testing

# protocol vectors (Python + cryptography)
python3 protocol/test-vectors/generate.py --check
# backends
(cd backend/go && go test -race ./...)
(cd backend/rust && cargo test --release)
# conformance suite against either backend
(cd backend/go && go run ./cmd/mcvoice-conformance -- ../rust/target/release/mcvoice-backend)
# client core + headless end-to-end tests against a real backend
(cd client && MCVOICE_BACKEND_BIN=/path/to/mcvoice-backend ./gradlew build)
# a Minecraft build
python3 tools/port-version/port.py 1.20.1 && (cd minecraft/fabric && ./gradlew build)

CI workflows:

Workflow	Purpose
ci.yml	Everything on main except Minecraft jars
backend.yml	Container images and GHCR
mc-build.yml	Per-version Minecraft builds
version-matrix.yml	Refreshes the version matrix
svc-interop.yml	Real Simple Voice Chat server check
release.yml	Releases
mc-probe.yml	API lookup for porting
mc-smoke.yml	Client runtime smoke test: starts the real client headlessly with the mod and joins a world (dispatch only)

Documentation

• Architecture
• Protocol overview and specification
• Proximity security
• Simple Voice Chat interoperability
• Version porting
• Backend deployment
• Releasing

Security and privacy

• No voice recording and no raw audio retention.
• No player IP addresses exposed to other clients.
• No exact positions in production logs.
• No Microsoft/Minecraft access tokens in any MCVoice packet.

Found a vulnerability? Please open a private security advisory on GitHub.

License and third parties

MIT, see LICENSE. Bundled: Concentus (pure-Java Opus, BSD-3-Clause), relocated to dev.mcvoice.thirdparty.concentus. Simple Voice Chat is a separate project by its authors. MCVoice is not affiliated with it and contains none of its code or assets. The interoperability layer is an independent implementation, tested against the unmodified SVC server.