How does this site change the URL of the browser without changing pages?

Question

If you go to this site http://www.20thingsilearned.com/ in Google Chrome and change pages, it will change the URL displayed in the browser, but seemingly not actually navigate to another page.

Opening the site in Firefox just uses plain old hash URLs. What makes them able to do this in Chrome?

Answer 1

They're using the new HTML5 history.pushState() and history.replaceState() methods.