VST2

VST2 is the legacy Steinberg plugin format. It's been superseded by VST3 but is still the format of choice for older Reaper projects, Ableton Live 10 and earlier, and FL Studio's "prefer VST2" setting. Truce ships clean-room C bindings (no Steinberg SDK headers) so the truce-vst2 crate itself is MIT/Apache-2.0 licensed.

#Status

Opt-in. Working on all three platforms. Tested in Reaper on macOS, Windows, and Linux; Ableton Live 11 on macOS; FL Studio on Windows.

#⚠️ Licensing

Steinberg deprecated the VST2 SDK in October 2018 and no longer issues new VST2 license agreements. Distributing VST2 plugins may require an existing Steinberg agreement.

Truce's clean-room C shim (truce-vst2/shim/vst2_shim.c) uses no Steinberg SDK headers and carries no Steinberg copyright, so the crate itself is redistributable under MIT/Apache-2.0. What is still licensed by Steinberg:

  • The VST trademark and logo.
  • The VST2 identifier codes you register (if any).
  • Hosting / display of VST2 plug-ins in Steinberg's own products.

If you're shipping a VST2 plugin commercially in 2026, consult counsel. For personal use, internal tooling, or open-source plugins targeting hobbyist users the risk is low — but this doc is not legal advice.

Enable this feature only if you understand the licensing implications.

#Enable

VST2 is opt-in. Either add it to [features].default in Cargo.toml or pass --vst2 to cargo truce.

[features]
default = ["clap", "vst3", "vst2"]
vst2 = ["dep:truce-vst2"]
cargo truce install --vst2

#Requirements

  • A C compiler. Xcode CLI tools (macOS), MSVC (Windows), or GCC/Clang (Linux). The shim is a single .c file.

No Steinberg SDK required.

#Install paths

Platform User (default) System (--system)
macOS ~/Library/Audio/Plug-Ins/VST/{Name}.vst/ /Library/Audio/Plug-Ins/VST/{Name}.vst/ (sudo)
Windows system† %PROGRAMFILES%\Steinberg\VstPlugins\{Name}.dll (admin)
Linux ~/.vst/{Name}.so same (Linux is user-only)

† = --user falls back to system silently. Windows VST2 has no agreed-upon per-user path that every host scans, so cargo truce install --user --vst2 lands at %PROGRAMFILES%\Steinberg\VstPlugins\ (Administrator shell required) and prints a one-line note.

Unlike VST3, VST2 has no bundle hierarchy on Windows / Linux — a single shared library file is the plugin. On macOS we wrap the dylib in a .vst bundle with Contents/MacOS/.

#Signing

  • macOS: codesigned with $TRUCE_SIGNING_IDENTITY on install.
  • Windows: Authenticode-signed at packaging time via signtool.
  • Linux: no signing.

#Build / install / package

cargo truce install --vst2
cargo truce build --vst2
cargo truce package --formats vst2

#Validate

cargo truce validate runs pluginval against installed VST2 bundles (strictness 5), same as VST3.

#Hosts

Host Platform Status
Reaper macOS / Windows / Linux working (Linux: plugin installs correctly; Reaper's browser may not surface it — investigation open)
Ableton Live 10 / 11 macOS / Windows working
FL Studio Windows working
Logic Pro — AU only, no VST2
Pro Tools — AAX only, no VST2

#Gotchas

  • Four-char plugin ID: fourcc in truce.toml becomes the VST2 unique ID (cast to int32). Must be stable across releases — hosts key project state on it. First character is traditionally uppercase ASCII to stay above the VST2 "manufacturer-reserved" cutoff.
  • No MIDI 2.0: VST2 has no UMP pipeline. Truce plugins will only see MIDI 1.0 events when loaded via VST2, even if the plugin's EventBody enum supports MIDI 2.0 variants on other formats.
  • No sample-accurate automation: VST2's parameter model is block-rate. If your plugin relies on ParamChange events landing between audio samples (CLAP, VST3), VST2 will only deliver them at block boundaries.
  • Reaper-Linux browser bug: VST2 bundles install to ~/.vst/ correctly, but Reaper for Linux may not surface them in its plugin browser. Workaround: symlink into Reaper's custom VST search path.