Facebook Callback appends '#_=_' to Return URL

Question

Facebook callback has started appending #_=_ hash underscore to the Return URL

Does anyone know why? What is the solution?

Answer 1

Facebook uses a frame and inside of it everything functions using AJAX communication. The biggest problem in this case is preserving the current page state. As far I understand, Facebook decided to use simulated anchors. This means if you clicked somewhere, they simulate that as an anchor inside of your page, and when the AJAX communication starts, they change the anchor bit of your URL as well.

This solution helps you normally when you try to reload the page (not ENTER, press F5), because your browser sends the whole URL with anchors to the Facebook server. Therefore Facebook picks up the latest state (what you see) and you are then able to continue from there.

When the callback returns with #_=_ it means that the page was in its basic state prior to leaving it. Because this anchor is parsed by the browser, you need not worry about it.