What is the MID file format?
.mid files are closely related to the .midi format - both are Standard MIDI File (SMF) sequences.
.mid files store musical performance events organized with precise timing. These events can describe:
- note pitch, velocity, and playback duration,
- volume, expression, and other controller values,
- instrument (program) changes across up to 16 channels.
It should be noted that .mid files do not contain audio data, only the event instructions necessary for proper playback by a synthesizer or soundfont engine. Because no audio samples are stored, the same .mid file can sound noticeably different across devices.
Files with the .mid extension can be used by music editing software applications as well as MIDI hardware devices and synthesizers. .mid files serve as a universal way to share musical compositions between programs - digital audio workstations, notation editors, and sequencers all support the format. On hardware devices, .mid files can be used to trigger instruments, change audio output parameters such as pitch or duration, and drive automated performances.
Internally, a .mid file uses a chunk-based binary structure: an MThd header chunk establishes the format type (0, 1, or 2), track count, and timing resolution, followed by one or more MTrk track chunks storing delta-time-stamped events. The .rmi variant wraps the same content in a RIFF container, while the .kar format extends .mid with embedded karaoke lyrics.
Security & safety
RISK: LOWA Standard MIDI File is passive event data with no embedded code or macros, so the format itself is low-risk. Historic concern: in 2012 a Windows MIDI parsing flaw (CVE-2012-0003) allowed code execution via a crafted MIDI in Windows Media Player - long since patched, so keep your OS/players updated. Otherwise the main "risk" is disappointment: a MIDI may sound thin or wrong because playback depends on the device's soundfont, not the file.
Format details
in a nutshell- Karaoke MIDI (.kar) - Same Standard MIDI File structure with lyric meta-events embedded for karaoke; often saved with a .mid extension too.
- RMID (RIFF MIDI) - A MIDI sequence wrapped in a RIFF container, sometimes with an embedded DLS soundbank; uses .rmi but occasionally .mid.
Programs that open MID files
Windows4 apps
VLC media player
Open-source Open the .mid; VLC plays MIDI using a bundled/soundfont synth (set a SoundFont in Preferences > Input/Codecs > MIDI for better sound). 
Windows Media Player
Built-in Double-click to play via the Windows built-in GS wavetable synth (no extra software needed). 
MuseScore
Open-source File > Open the .mid to view it as sheet music, edit notes/instruments, and export to MP3/WAV/PDF/MusicXML. 
macOS3 apps
QuickTime Player
Built-in Older macOS QuickTime plays MIDI; on modern macOS use VLC or MuseScore instead if QuickTime declines it. 
Apple Logic Pro
Paid Import the MIDI into a project to assign software instruments and produce/render audio. 
Linux3 apps
TiMidity++
Open-source Play from the terminal: 'timidity song.mid' (renders MIDI with a soundfont/patch set). 
Android1 app
Online Sequencer / signal (web MIDI editors)
Free Upload the .mid to play and edit it in the browser without installing anything. Technical details
deep spec| File encoding | Binary, big-endian byte order |
| File signature (magic bytes) | `4D 54 68 64` - ASCII `MThd` at byte offset 0, followed by a 4-byte chunk length (`00 00 00 06`) |
| Container structure | Chunk-based: `MThd` header chunk followed by one or more `MTrk` track chunks |
| Format types | Format 0 - single multi-channel track; Format 1 - multiple synchronous tracks; Format 2 - independent pattern sequences |
| MIDI channel capacity | Up to 16 simultaneous channels per file, each assignable to a different instrument or voice |
| Timing resolution | Set by the `division` field in `MThd`; expressed as ticks per quarter note (e.g., 480 PPQ) or SMPTE timecode frames |
| Event delta-time encoding | Variable-length quantity (VLQ) - encodes inter-event timing gaps using 7 bits per byte with an MSB continuation flag |
| MIME type | `audio/midi`; also recognized as `audio/x-midi` and `audio/sp-midi` |
| Typical file size | 1 KB - 100 KB; a few minutes of music is usually well under 50 KB because no audio samples are stored |
| Compression | None; events are inherently compact through binary opcodes and VLQ delta-time encoding |
| Meta events | Non-sound metadata embedded in tracks: tempo (microseconds per beat), time signature, key signature, track name, lyrics, copyright, and end-of-track markers |
| Developer / maintainer | MIDI Manufacturers Association (MMA) and AMEI (Association of Musical Electronics Industry) |
| MIDI 2.0 compatibility | `.mid` encodes MIDI 1.0 messages; the MIDI 2.0 protocol (2020) uses different container formats - `.mid` files remain in widespread active use |
| Released | Standard MIDI File 1.0 published 1988 (MIDI protocol 1983) |
| Latest version | SMF 1.0 (stable since 1988); MIDI 2.0 protocol 2020 uses .midi2/clips, not .mid |
| Open standard | Yes · royalty-free |
| Specification | midi.org |
MID conversions
Community Q&A
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