h5o is an implementation of the HTML5 outline algorithm.

In your browser

• Chrome extension
  • Install from Chrome Store
  • Install a standalone crx
    (note that while the signing key for the crx is encrypted, the password is “known” to Travis)
  • Source code

• Bookmarklet: https://h5o.github.io/bookmarklet.html

  • Installation details for common browsers.
  • Internet Explorer not supported.
  • Source code

Javascript library

npm install h5o

var HTML5Outline = require("h5o");
var outline = HTML5Outline(document.body);
console.log(outline.asHTML());

More details in the readme.