MusicXML Validator

What the validator checks

First, whether the file is well-formed XML at all. Then every element and attribute against the official MusicXML 4.0 schema (XSD) of the W3C Music Notation Community Group: whether each is allowed where it stands, in the right order, with values the schema accepts. Every error comes with its line in the file. The check runs with libxml2, the XML library behind xmllint, compiled to run in your browser.

The validator also checks what every score needs: a score-partwise or score-timewise root, a part list, at least one part, measures in every part, notes and attributes. A file that passes is one that notation software can start reading.

On request it also lists what the score contains: articulations, dynamics, slurs and ties, ornaments, tempo and time signatures, voices and, for vocal parts, lyrics. None of those is required by MusicXML.

Questions

Is this full validation against the MusicXML schema?

Yes: every file is checked against the complete MusicXML 4.0 schema. Files written for earlier versions are checked against 4.0 too. Almost everything valid in MusicXML 3.1 is valid in 4.0; one exception the 4.0 change notes name is an empty multiple-rest element, which 4.0 no longer allows.

My file has schema errors. Will it still open?

Usually: most notation programs read past a few errors. But a program may then drop or misread the element in question, so the list shows what to fix, starting with the line of each error.

Is my file uploaded?

No. The checks run in your browser tab, and the file never leaves your computer.

The file is valid, but it looks wrong in my program. Why?

Valid MusicXML can still carry export mistakes: a piano split into two unnamed parts, the title written as an ordinary text, lyrics without hyphens. Open it in the Sheet Music Viewer to see how it renders.