URL on a landing page and URL after logged in

Question

Why are a landing page and a page after user logs in same on most websites? For example, on Facebook the landing page url is https://www.facebook.com . After you logs into FB you are redirected to Home but same url as above: https://www.facebook.com .

Does it mean Facebook uses the same file (eg index.html/index.php) for the landing page and the the page after user logs in?

Thanks!

Answer 1

The webserver can serve different content based on many factors; cookies in this case. The URL you see in the bar doesn't have to correlate the same path on some server - the application can dynamically accept or reject any path (it's just a string). In PHP, you can do this with a front controller which is pattern used by many frameworks like Symphony and Laravel.

As for why Facebook does this, they probably just think it looks better that way.