How relative link in href working?

Question

I have a problem relating to relative links in href. To make a long story short, I think an example is the best way to get what's going on.

On tinhte.vn/threads/300021/, it is a discussion forum, to go to the page 2, we click on [2].

I view source code of [2], its content is <a href="threads/300021/page-2" class="">2</a>. If I do not misunderstand about relative links, this will append threads/30021/page-2 after the current link, which is tinhte.vn/threads/30021/, and we have the link like this:

tinhte.vn/threads/300021/threads/300012/page-2

But in practice, when I do in the browser, mine is chrome, the link is:

tinhte.vn/threads/300012/page-2

Anyone please explain why?

Sorry, due to the spam prevention, I cannot post direct link.

Thanks in advance.

Answer 1

The link will correctly go to tinhte.vn/threads/300021/threads/300012/page-2 as you guessed. However, looking at the response from a request to that url we can see that the page redirects to another url. I used web-sniffer to quickly see the raw response from the server.

The interesting part of the response is this:

<input type="hidden" name="redirect" value="/threads/300021/page-2"/>

The browser will react to this and navigate to the specified URL. Hence the observed behaviour.

Read more about redirects here.