Plugin Formats

Supported Formats

iPlug2 supports all major plugin formats through a unified API abstraction. Write your code once, compile to multiple formats.

VST3

Steinberg’s modern standard

AUv2

macOS/iOS (legacy)

AUv3

macOS/iOS (modern)

AAX

Avid Pro Tools

CLAP

Modern open standard

WAM

Web Audio Modules

VST2 is also supported but deprecated due to licensing. Not recommended for new projects.

Format Comparison

Feature	VST3	AUv2	AUv3	AAX	CLAP	WAM
Windows	✅	❌	❌	✅	✅	✅
macOS	✅	✅	✅	✅	✅	❌
iOS	❌	❌	✅	❌	❌	❌
Linux	✅	❌	❌	❌	✅	❌
Web	❌	❌	❌	❌	❌	✅
Sidechain	✅	✅	✅	✅	✅	✅
MIDI I/O	✅	✅	✅	✅	✅	✅
Multi-bus	✅	✅	✅	✅	✅	✅
Sample Accurate	✅	⚠️	✅	⚠️	✅	✅
Open Standard	❌	❌	❌	❌	✅	✅

VST3

Implemented in IPlugVST3.h

Steinberg’s VST3 is the most widely supported plugin format across DAWs.

Architecture

VST3 uses a separated processor/controller architecture:

class IPlugVST3 : public IPlugAPIBase,
                  public IPlugVST3ProcessorBase,     // Audio processing
                  public IPlugVST3ControllerBase,    // UI/parameters
                  public Steinberg::Vst::SingleComponentEffect

Features
Platform Support
Configuration

VST3 Capabilities

Sample-accurate automation
Multiple input/output buses
Sidechain support
Context menus in host
Channel context information
Preset management
MIDI mapping

// VST3-specific: MIDI CC mapping
Steinberg::tresult getMidiControllerAssignment(
  Steinberg::int32 busIndex, 
  Steinberg::int16 channel,
  Steinberg::Vst::CtrlNumber midiCCNumber, 
  Steinberg::Vst::ParamID& tag
);

Platforms

✅ Windows (64-bit)
✅ macOS (Intel & Apple Silicon)
✅ Linux

File Extensions

.vst3 - VST3 bundle (all platforms)

Installation Paths

Windows: C:\Program Files\Common Files\VST3\
macOS: /Library/Audio/Plug-Ins/VST3/
Linux: ~/.vst3/

config.h

#define VST3_SUBCATEGORY "Fx"
// Options: "Fx", "Instrument", "Analyzer", etc.

#define PLUG_CHANNEL_IO "1-1 2-2"
// Mono-to-mono and stereo-to-stereo

#define PLUG_LATENCY 0
// Report latency in samples

See VST3 categories: Fx, Instrument, Spatial, Analyzer, Delay, Distortion, Dynamics, EQ, Filter, Mastering, Modulation, Restoration, Reverb, Surround, Tools

VST3 Specifics

VST3 has a separated state model. Use SerializeVST3CtrlrState() and UnserializeVST3CtrlrState() for UI-only state if needed (rare).

// Usually you only need this
virtual bool SerializeState(IByteChunk& chunk) const {
  return SerializeParams(chunk);
}

// VST3-specific controller state (rare)
virtual bool SerializeVST3CtrlrState(IByteChunk& chunk) const {
  return true;  // Usually not needed
}

Audio Unit v2 (AUv2)

Implemented in IPlugAU.h

Apple’s legacy Audio Unit format for macOS. Still widely used but being replaced by AUv3.

Architecture

class IPlugAU : public IPlugAPIBase,
                public IPlugProcessor

Features
Platform Support
Configuration

AUv2 Capabilities

macOS native format
Parameter units (dB, Hz, etc.)
Preset management
Factory preset support
Multi-bus I/O
Sidechain inputs

// AUv2 parameter units affect host display
GetParam(kFreq)->InitFrequency("Frequency", 1000., 20., 20000.);
// Automatically sets EParamUnit::kUnitFrequency

Parameter Units

enum EParamUnit {
  kUnitPercentage, kUnitSeconds, kUnitMilliseconds,
  kUnitDB, kUnitFrequency, kUnitCents, kUnitMIDINote,
  kUnitBPM, kUnitPan, kUnitPhase, kUnitDegrees,
  kUnitLinearGain, kUnitOctaves, kUnitRate,
  kUnitCustom  // Use custom label
};

Platforms

✅ macOS only (Intel & Apple Silicon)
❌ iOS (use AUv3)

File Extensions

.component - AUv2 bundle

Installation Paths

macOS: /Library/Audio/Plug-Ins/Components/
User: ~/Library/Audio/Plug-Ins/Components/

AUv2 plugins must be signed and notarized for macOS 10.15+ (Catalina and later).

config.h

#define PLUG_TYPE 0
// 0 = Effect, 1 = Instrument, 2 = MIDI Effect

#define AUV2_ENTRY IPlugEffect_Entry
#define AUV2_ENTRY_STR "IPlugEffect_Entry"
#define AUV2_FACTORY IPlugEffect_Factory
#define AUV2_VIEW_CLASS IPlugEffect_View
#define AUV2_VIEW_CLASS_STR "IPlugEffect_View"

AUv2 Types (derived from PLUG_TYPE):

'aufx' - Audio effect
'aumu' - Music device (instrument)
'aumf' - MIDI effect
'augn' - Generator (no input)

AUv2 Specifics

// Get track name (AUv2 & AAX support this)
void GetTrackName(WDL_String& str) override;

// AUv2 uses component manager on older macOS
static OSStatus IPlugAUEntry(ComponentParameters* pParams, void* pPlug);

Audio Unit v3 (AUv3)

Implemented in IPlugAUv3.h

Apple’s modern Audio Unit format for macOS and iOS with app extensions.

Architecture

class IPlugAUv3 : public IPlugAPIBase,
                  public IPlugProcessor

Features
Platform Support
Configuration

AUv3 Capabilities

App extension architecture (sandbox)
iOS support (iPad/iPhone)
Sample-accurate parameter events
Inter-app audio
State saving/restoration
SwiftUI integration possible

// AUv3 uses event-based processing
void ProcessWithEvents(
  AudioTimeStamp const* timestamp,
  uint32_t frameCount,
  AURenderEvent const* events,
  ITimeInfo& timeInfo
);

Platforms

✅ macOS 10.11+ (Intel & Apple Silicon)
✅ iOS 9+
❌ Windows, Linux

Distribution

Requires host app (container)
Distributed via App Store or direct
Can include iOS app with AUv3

Example: AUv3 on iPad

MyPlugin.app/
  PlugIns/
    MyPluginAU.appex  ← AUv3 extension

config.h

#define APP_COPY_AUV3 1
// Copy AUv3 to app bundle

#define BUNDLE_NAME "IPlugEffect"
#define BUNDLE_MFR "AcmeInc"
#define BUNDLE_DOMAIN "com"
// Bundle ID: com.AcmeInc.IPlugEffect

AUv3 requires:

App entitlements
Audio component description in Info.plist
Code signing
Sandboxing (on iOS)

AUv3 Specifics

AUv3 uses parameter addresses instead of indices. iPlug2 handles the mapping automatically.

// Internal mapping between param indices and AU addresses
void AddParamAddress(int paramIdx, uint64_t paramAddress);
uint64_t GetParamAddress(int paramIdx);
int GetParamIdx(uint64_t paramAddress);

AAX

Implemented in IPlugAAX.h

Avid’s plugin format for Pro Tools. Requires AAX SDK (free registration required).

Architecture

class IPlugAAX : public IPlugAPIBase,
                 public IPlugProcessor,
                 public AAX_CIPlugParameters

Features
Platform Support
Configuration

AAX Capabilities

Native Pro Tools integration
AudioSuite (offline processing)
Stem formats (multi-channel)
Track naming
Pro Tools automation
Parameter highlighting

// AAX-specific: parameter highlighting in Pro Tools
AAX_Result SetControlHighlightInfo(
  AAX_CParamID iParameterID,
  AAX_CBoolean iIsHighlighted,
  AAX_EHighlightColor iColor
);

Platforms

✅ Windows (64-bit)
✅ macOS (Intel & Apple Silicon)
❌ iOS, Linux

File Extensions

.aaxplugin - AAX bundle

Installation Paths

Windows: C:\Program Files\Common Files\Avid\Audio\Plug-Ins\
macOS: /Library/Application Support/Avid/Audio/Plug-Ins/

AAX plugins must be signed by Avid (PACE iLok). Development signing available for testing.

config.h

#define AAX_TYPE_IDS 'IEF1', 'IEF2'
#define AAX_TYPE_IDS_AUDIOSUITE 'IEA1', 'IEA2'
#define AAX_PLUG_MFR_STR "Acme"
#define AAX_PLUG_NAME_STR "IPlugEffect\nIPEF"
#define AAX_PLUG_CATEGORY_STR "Effect"
#define AAX_DOES_AUDIOSUITE 1

AAX Categories: EQ, Dynamics, PitchShift, Reverb, Delay, Modulation, Harmonic, NoiseReduction, Dither, SoundField, Effect

AAX Specifics

// AAX parameter IDs are offset by 1
const int kAAXParamIdxOffset = 1;

// AAX processing is page-table based
// iPlug2 handles this automatically

// Get track name (works in Pro Tools)
void GetTrackName(WDL_String& str) override;

CLAP

Implemented in IPlugCLAP.h

CLever Audio Plug-in - modern open-source plugin standard created by the u-he team.

Architecture

class IPlugCLAP : public IPlugAPIBase,
                  public IPlugProcessor,
                  public ClapPluginHelper

Features
Platform Support
Configuration

CLAP Capabilities

Sample-accurate parameter automation
Modern C++ design
Open standard (no licensing)
Note expressions (MPE-like)
Polyphonic modulation
Voice info/management
Extensible architecture

// CLAP uses event-based parameter changes
struct ParamToHost {
  enum class Type { Begin, Value, End };
  Type mType;
  int mIdx;
  double mValue;
};

CLAP has the most modern feature set: note expressions, polyphonic modulation, and flexible extension mechanism.

Platforms

✅ Windows (64-bit)
✅ macOS (Intel & Apple Silicon)
✅ Linux
❌ iOS, Web

File Extensions

.clap - CLAP bundle (all platforms)

Installation Paths

Windows: C:\Program Files\Common Files\CLAP\
macOS: /Library/Audio/Plug-Ins/CLAP/
Linux: ~/.clap/ or /usr/lib/clap/

Host Support

Bitwig Studio (full support)
Reaper (full support)
FL Studio (in development)
Many more adopting

config.h

#define CLAP_MANUAL_URL "https://example.com/manual.pdf"
#define CLAP_SUPPORT_URL "https://example.com/support"
#define CLAP_DESCRIPTION "A simple audio effect"
#define CLAP_FEATURES "audio-effect"
// Features: "audio-effect", "instrument", "synthesizer",
//           "delay", "reverb", "distortion", etc.

See full feature list: CLAP features

CLAP Specifics

// CLAP uses parameter gestures (begin/change/end)
void BeginInformHostOfParamChange(int idx) override;
void InformHostOfParamChange(int idx, double normalizedValue) override;
void EndInformHostOfParamChange(int idx) override;

// CLAP tail size is dynamic
void SetTailSize(int tailSize) override;

WAM (Web Audio Modules)

Implemented in IPlugWAM.h

Web Audio Modules run in browsers using WebAssembly. Perfect for demos and web-based DAWs.

Architecture

class IPlugWAM : public IPlugAPIBase,
                 public IPlugProcessor,
                 public WAM::Processor  // WebAssembly processor

Features
Platform Support
Configuration

WAM Capabilities

Runs in web browsers
WebAssembly (WASM) compilation
Web Audio API integration
Real-time audio in browser
MIDI support
SysEx support
Message passing (JS ↔ C++)

// WAM-specific message handling
void onMessage(char* verb, char* res, double data) override;
void onMessage(char* verb, char* res, char* data) override;
void onParam(uint32_t idparam, double value) override;

config.h

// Same config as other formats
#define PLUG_NAME "IPlugEffect"
#define PLUG_CHANNEL_IO "2-2"

// WAM compiles to WebAssembly
// Build with Emscripten:
// emcc -O3 -s WASM=1 ...

UI Options for WAM:

IGraphics (compiled to WebGL)
Web UI (HTML/CSS/JavaScript)
Canvas-based custom UI

WAM Specifics

WAM runs in AudioWorkletGlobalScope (sandboxed). Limited access to system resources.

// WAM lifecycle
const char* init(uint32_t bufsize, uint32_t sr, void* pDesc) override;
void terminate() override;
void resize(uint32_t bufsize) override;

// WAM uses different message system (no direct MIDI send)
void SetLatency(int samples) override {}  // Not supported
bool SendMidiMsg(const IMidiMsg& msg) override { return false; }

Choosing a Format

Maximum Compatibility

VST3 + AUv2Covers Windows, macOS, and most DAWs.

Pro Tools

AAX + VST3 + AUv2Adds Pro Tools support (requires AAX SDK and signing).

Modern/Future

CLAP + VST3CLAP has best features, VST3 for compatibility.

iOS/Mobile

AUv3Only option for iOS. Can include in app.

Web/Demos

WAMShare plugins via URL, no installation.

Everything

All FormatsiPlug2 can compile to all formats from same code!

Multi-Format Build System

iPlug2 uses duplicate projects for each format:

MyPlugin/
  MyPlugin.cpp
  MyPlugin.h
  config.h
  
  projects/
    MyPlugin-app.vcxproj         (Standalone)
    MyPlugin-vst3.vcxproj        (VST3)
    MyPlugin-au.xcodeproj        (AUv2)
    MyPlugin-auv3.xcodeproj      (AUv3)
    MyPlugin-aax.vcxproj         (AAX)
    MyPlugin-clap.vcxproj        (CLAP)
    MyPlugin-wam.vcxproj         (WAM)

The duplicate.py script creates these projects automatically from templates. Run it once, then build any format.

Platform-Specific Notes

Windows
macOS
iOS
Linux

Available Formats:

VST3
AAX
CLAP
Standalone App

Visual Studio Required:

VS 2019 or later
Windows 10 SDK

Code Signing:

Recommended for distribution
Not required for development

Next Steps

Architecture

Understand the plugin architecture and lifecycle

Parameters

Learn parameter types and automation

Audio Processing

Master ProcessBlock and real-time audio

Project Structure

Explore config.h and project organization

​Supported Formats

VST3

AUv2

AUv3

AAX

CLAP

WAM

​Format Comparison

​VST3

​Architecture

​VST3 Specifics

​Audio Unit v2 (AUv2)

​Architecture

​AUv2 Specifics

​Audio Unit v3 (AUv3)

​Architecture

​AUv3 Specifics

​AAX

​Architecture

​AAX Specifics

​CLAP

​Architecture

​CLAP Specifics

​WAM (Web Audio Modules)

​Architecture

​WAM Specifics

​Choosing a Format

Maximum Compatibility

Pro Tools

Modern/Future

iOS/Mobile

Web/Demos

Everything

​Multi-Format Build System

​Platform-Specific Notes

​Next Steps

Architecture

Parameters

Audio Processing

Project Structure

Supported Formats

Format Comparison

VST3

Architecture

VST3 Specifics

Audio Unit v2 (AUv2)

Architecture

AUv2 Specifics

Audio Unit v3 (AUv3)

Architecture

AUv3 Specifics

AAX

Architecture

AAX Specifics

CLAP

Architecture

CLAP Specifics

WAM (Web Audio Modules)

Architecture

WAM Specifics

Choosing a Format

Multi-Format Build System

Platform-Specific Notes

Next Steps