How to Sniff Raw MIDI Packets on macOS and Windows

Sniffing raw MIDI packets is an essential troubleshooting step for musicians, hardware developers, and audio engineers looking to diagnose communication faults between controllers, synthesizers, and software. This article outlines the premier software utilities used on macOS and Windows to intercept, log, and analyze raw MIDI data streams in real time.

Top MIDI Sniffing Utilities for macOS

1. Snoize MIDI Monitor

Snoize MIDI Monitor is the definitive standard for inspecting MIDI traffic on macOS. It integrates seamlessly with CoreMIDI to track inputs from physical hardware, network sessions, and virtual MIDI sources generated by other applications.

• Key Capabilities: Displays raw hexadecimal bytes alongside decoded event descriptions (Note-On, Control Change, Pitch Bend). It allows deep filtering to isolate specific channels or message types, and features a spy mode to monitor traffic routed to specific destination applications.

2. Hexler Protokol

Protokol is a modern, lightweight utility designed for monitoring control protocols, including MIDI, OSC, Art-Net, and Gamepad inputs.

• Key Capabilities: Highly responsive with a minimal graphical interface. It outputs timestamped, color-coded event feeds alongside exact byte representations, making it an excellent choice for modern macOS environments, including native Apple Silicon support.

Top MIDI Sniffing Utilities for Windows

1. MIDI-OX

MIDI-OX is the long-standing, multi-purpose diagnostic tool for 32-bit and 64-bit Windows systems. While its user interface is dated, its diagnostic power remains unmatched for legacy and standard MIDI troubleshooting.

• Key Capabilities: Features a dedicated Input Monitor window that prints time-stamped status bytes, data bytes, channels, and event types. It includes deep diagnostic tools for System Exclusive (SysEx) dumps, a built-in data generator to test device responsiveness, and route-mapping capabilities.

2. MIDIberry

Available via the Microsoft Store, MIDIberry provides an updated, straightforward interface for Windows 10 and 11 users who require quick packet validation without complex routing setups.

• Key Capabilities: Automatically detects connected USB-MIDI and Bluetooth LE MIDI interfaces, printing incoming data lines sequentially. It displays channel assignments, note values, and raw parameters with minimal setup.

Cross-Platform Alternatives

1. Pocket MIDI

Pocket MIDI is an effective, free diagnostic monitor available for both macOS and Windows.

• Key Capabilities: Functions symmetrically as both an input sniffer and an output transmitter. The main interface splits into an incoming monitor pane and an outgoing message builder, permitting rapid, bidirectional testing of raw MIDI streams and SysEx blocks.

2. Wireshark (with USBPcap or Network Capture)

For deep protocol-level analysis, Wireshark can capture MIDI data before it reaches the operating system's audio subsystem.

• USB-MIDI: By pairing Wireshark with USBPcap on Windows or native USB capture on macOS, engineers can capture the underlying USB packets containing encapsulated MIDI commands.
• RTP-MIDI (AppleMIDI): For network-based MIDI setups over Ethernet or Wi-Fi, Wireshark decodes RTP-MIDI payloads directly to examine packet loss, jitter, and timestamp synchronization.