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Professional piano roll
Drag notes to change pitch and length, click to add new notes, zoom in for surgical precision. Grid snap on or off, your call.
The Online MIDI Editor
Free Online MIDI Editor — Piano Roll, Quantize, No Install
Edit .mid files with studio-grade tools — directly in your browser. Drag notes on a professional piano roll, quantize timing, change velocity, transpose, edit per-track, and export a clean .MID — no software install, no upload, no sign-up.
What you get
A piano roll that does what a real DAW does
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Smart quantization
Snap loose performance timing to a clean rhythmic grid from 1/4 to 1/32 — fix sloppy takes without re-recording.
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Velocity & dynamics
Edit per-note velocity to humanize a part. Drag velocity bars below the piano roll, or paint a curve for dynamic shaping.
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Transpose & change tempo
Move the whole piece up or down by semitones, or override the BPM. Use it to play in a singer's key or speed-up practice loops.
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Multi-track editing
Solo, mute, hide or change the instrument on any track. Each track gets its own visibility, color and channel control.
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Standard .MID export
Round-trip safely: import .mid or .kar, edit, export a clean Type 0 or Type 1 MIDI that opens in every DAW and notation app.
How it works
From .mid file to edited export in minutes
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Import your MIDI
Drag and drop a .mid or .kar file, or click to browse. The file is parsed instantly in your browser — tracks, tempo and key signature appear on the timeline.
- 02
Edit notes on the piano roll
Click empty grid cells to add notes. Drag existing notes to move them in pitch or time. Stretch the right edge to change duration.
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Refine timing & velocity
Select a range of notes and hit Quantize to snap to a grid. Drag the velocity lane to add expression — louder hits, quieter passes.
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Edit per track
Solo a part to focus, mute the drums, or hide a track to declutter the view. Swap an instrument when you need a different feel.
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Export the .MID
Click Export. A standard MIDI file is downloaded locally — no watermarks, no account required. Open it in your DAW and keep working.
Who it's for
Built for four kinds of MIDI editing
Producers sketching ideas
Quick fixes before DAW import
You bounced a MIDI from a hardware sequencer and need to clean up timing before dropping it in Ableton. Quantize, transpose, export — 90 seconds.
Students & teachers
Edit practice files
Slow down the BPM, transpose to a friendlier key, mute the right hand to play along with the left. Re-export for the next lesson.
Composers in a browser
No DAW handy
You're on a school computer or a friend's laptop. No Logic, no Ableton, no Cubase. Sketch an idea in the piano roll and email yourself the .mid.
Game audio & sample makers
Hand-edit MIDI for tools that demand it
Sample mappers, soundfont players and game audio middleware often expect specific MIDI structures. Use this to surgically reshape a file.
How it compares
MidiToolbox vs desktop MIDI editors
| Feature | MidiToolbox | Signal | MidiEditor | DAWs |
|---|---|---|---|---|
| Install required | No | No (browser) | Yes | Yes |
| Piano roll | Yes | Yes | Yes | Yes |
| Quantization | 1/4 to 1/32 | Yes | Yes | Yes |
| Multi-track edit | Yes | Yes | Yes | Yes |
| Works on iPad / mobile | Yes | Limited | No | Some |
| Price | Free | Free | Free | $60—$700 |
DAWs win for full music production. But for surgical MIDI edits — quantize a passage, transpose a section, fix a velocity curve — a browser editor opens the file faster than your DAW launches.
Common questions
Things people ask before editing
If something's off
Common editing issues and quick fixes
- Notes drift off the grid after editing
- Grid snap is off. Toggle the snap button in the toolbar and pick a grid value (typically 1/16). New notes and dragged notes will now align to the grid.
- Quantize made the part feel robotic
- You quantized to too tight a grid. Try a looser grid (1/8 instead of 1/16), or use partial quantize: select only the worst-offending notes instead of the whole track.
- Exported .mid sounds different in my DAW
- Most DAWs ignore the instrument metadata in a MIDI file and load a default piano patch. This is normal. Assign instruments inside your DAW after import — the notes themselves are correct.
- Can't see all tracks
- A track may be hidden. Open the track list panel on the left, look for the hidden eye icon next to a track name, and click to make it visible again.
Under the hood
Technical specs
- Supported import
- .mid, .midi, .kar (Type 0 & Type 1)
- Export format
- Standard MIDI (Type 0 & Type 1)
- Polyphony
- Unlimited
- Quantize grid
- 1/4 to 1/32 + chord detect
- Tempo range
- 30 — 240 BPM
- Processing
- 100% local, no upload
Keep going
Related MIDI tools
MIDI Player
Preview the edited MIDI with BPM and loop controls before exporting to your DAW.
Open toolMIDI Converter
Render the edited .mid into MP3 or WAV with a SoundFont — useful for quick demos.
Open toolMIDI Analyzer
Inspect tempo, time signature, key, instruments and duration of any MIDI file.
Open toolPrivacy & licensing
All editing happens locally in your browser using WebAudio and IndexedDB. Your MIDI files stay on your device — we have no way to read them. You are responsible for ensuring you have the right to edit, share or redistribute the files you use.