midiviewer.io Local by default

MIDI Editor Online

Select, transpose, quantize, and export MIDI. Your file stays in your browser.

LOCAL MIDI CORRECTION DESK

Fix the notes you already have.

Select notes, delete mistakes, transpose a passage, tighten starts to a musical grid, change the whole tempo, and export a new Standard MIDI file.

.mid or .midi · local session · no sign-in
The practical guide

A focused editor for precise corrections

Many MIDI edits are smaller than a production session. A passage may be in the wrong key, a few notes may need removing, or a loosely played phrase may need its starts aligned to a musical grid. This editor keeps those corrections in one local browser workspace.

Selection is the safety boundary. Delete, transpose, and quantize affect only the highlighted notes. Quantization moves note starts while preserving their durations, and transposition rejects the whole operation if any selected note would leave the valid MIDI pitch range.

After every edit, the preview engine reloads the current in-memory MIDI. The sound you hear and the file you download therefore come from the same event data. Undo and redo keep the last 50 operations available during the open session.

What you can learn

Safe selection

Single, additive, box, and select-all workflows make the affected notes explicit.

Paired deletion

Removing a note deletes its matching note-on and note-off without leaving a hanging voice.

Bounded transpose

Move selected notes by semitone or octave while enforcing the MIDI 0–127 pitch range.

Start quantization

Snap selected starts to 1/4, 1/8, 1/16, or 1/32 without changing note length.

Tempo scaling

Scale every tempo change together, preserving the shape of a multi-tempo performance.

Standard MIDI export

Write a new .mid while preserving tracks, programs, controllers, SysEx, and untouched metadata.

Made for real files

Small edits that do not need a full DAW

  • Remove an accidental note before sharing a practice file.
  • Transpose a melody or selected passage into a more comfortable key.
  • Tighten note starts from a live performance to a simple rhythmic grid.
  • Slow or accelerate an entire tempo map while preserving its relative changes.
  • Preview corrections and export a clean Standard MIDI file for a DAW or notation app.
Questions, answered

Before you open a file

Can I edit MIDI files online for free?

Yes. Selection, deletion, transposition, quantization, tempo scaling, preview, undo, redo, and MIDI download are free and require no account.

Does editing upload my MIDI file?

No. The Editor reads, changes, previews, and writes the Standard MIDI file in your browser. It does not use the audio conversion upload API.

What does Quantize change?

Quantize moves the starts of selected notes to the nearest chosen grid from 1/4 through 1/32. Their durations remain unchanged.

What is not included in this editor?

This focused first version does not add notes, drag timing, resize durations, edit velocity or controllers, or restructure tracks.