What is the SMF file format?
Files with the .smf extension contain MIDI - Musical Instrument Digital Interface - sequence data. SMF files store complete MIDI playback instructions for hardware synthesizers, software sequencers, and MIDI-capable applications. Unlike audio formats such as .wav or .mp3, SMF files do not contain any sampled audio data. For this reason, an SMF file is significantly smaller than comparable audio files and far easier to edit note-by-note in a DAW or sequencer. The SMF standard specification was first published in 1988 by the MIDI Manufacturers Association (MMA), and the format has remained stable since.
Contents of SMF - Standard MIDI File
An SMF file, more commonly saved with the .mid extension, can contain instructions for audio devices to generate sound, including:
- MIDI notes (pitch and velocity),
- volume and pan control,
- instrument track assignments,
- additional effects such as reverb or pitch bend.
The format also allows additional information to be stored, such as tempo markings, time signatures, lyrics, and copyright metadata. Each SMF file is divided into a header (MThd) followed by one or more track chunks (MTrk).
Using SMF files to share data
The MIDI standard was designed for audio data portability between programs and devices. Format 0 supports only a single merged track, while Format 1 stores multiple synchronous tracks and is the most widely used type. Format 2 stores independent asynchronous patterns and is rare in practice. SMF files are supported by sequencers and DAWs such as MuseScore, Cubase, Logic Pro, and Digital Performer, as well as media players including VLC.
Security & safety
RISK: LOWStandard MIDI Files contain passive event data with no executable code. Historically CVE-2012-0003 allowed code execution via a malformed MIDI in Windows Media Player - patched long ago, but keep players updated. Otherwise a .smf is safe data.
Format details
in a nutshell- Simple Machine Forum backup - Some bulletin board software uses .smf for forum database export files - plain text/SQL, completely unrelated to MIDI.
Programs that open SMF files
Windows3 apps
VLC media player
Open-source Open the .smf file - VLC plays MIDI using a bundled synth (set a soundfont in Preferences > Input/Codecs > MIDI for better quality). 
Windows Media Player
Built-in Double-click to play via the Windows built-in GS wavetable synthesizer. 
MuseScore
Open-source File > Open the .smf to view as editable sheet music; export to MP3/WAV/PDF/MusicXML. 
macOS3 apps
QuickTime Player
Built-in Open the .smf file to play; older macOS plays MIDI natively. On modern macOS use VLC or MuseScore if QuickTime declines it. 
Apple Logic Pro
Paid Import the MIDI/SMF into a Logic project to add software instruments and produce audio. 
Linux2 apps
Android1 app
Signal (web MIDI editor)
Free Upload the .smf to play and edit it in the browser without installing anything. Technical details
deep spec| Magic bytes | `MThd` (hex 4D 54 68 64) at offset 0 - MIDI header chunk identifier |
| Header chunk structure | `MThd` + 4-byte length `00 00 00 06` + format type (2 bytes) + track count (2 bytes) + timing division (2 bytes) |
| Track chunk magic | `MTrk` (hex 4D 54 72 6B) begins each track chunk |
| Byte order | Big-endian for all multi-byte integers |
| Format types | 0 (single merged track), 1 (multi-track synchronous - most common), 2 (multi-track asynchronous - rare) |
| Timing resolution | Set by division field in header (e.g. 480 ticks/quarter note); tempo specified by `FF 51` meta-event in microseconds/beat |
| Typical file size | 1 KB - 100 KB; a complete multi-track song usually under 50 KB |
| Compression | None; delta-time uses variable-length quantity (VLQ) encoding for compactness, not data compression |
| Audio content | Stores MIDI event instructions (note on/off, velocity, program change, controller), not sampled waveforms |
| MIDI channels | Up to 16 simultaneous channels per file; channel 10 reserved for percussion by General MIDI convention |
| Meta-events | Tempo (`FF 51`), time signature (`FF 58`), track name (`FF 03`), lyrics (`FF 05`), copyright, end-of-track (`FF 2F`) |
| MIME type | `audio/midi`; also recognized as `audio/x-midi` and `audio/sp-midi` |
| Released | 1988 (SMF 1.0 specification) |
| Latest version | SMF 1.0 (stable since 1988; unchanged format) |
| Open standard | Yes · royalty-free |
| Specification | midi.org |
SMF conversions
Community Q&A
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