Score In URL lets you write your sheet music in ABC Notation, and share it through a URL, where all the information is self-contained. It's heavily inspired by the great project: Hashify, which does the same thing with Markdown documents.
Score In URL privacy-friendly, as there is nothing stored on a remote server. This website is, in fact, hosted on GitHub Pages, with no backend whatsoever.
Score In URL is free and open source, under the MIT license. You can find the source code on GitHub.
ABC Notation
ABC Notation is a way to write sheet music with plain text. You can learn more about it, by reading the full documentation, or use this cheat sheet as a quick reference.