HTML 5 Is it br br or br

Question

I've tried checking other answers, but I'm still confused — especially after seeing W3schools HTML 5 reference.

I thought HTML 4.01 was supposed to "allow" single-tags to just be <img> and <br>. Then XHTML came along with <img /> and <br /> (where someone said that the space is there for older browsers).

Now I'm wondering how I'm supposed to format my code when practicing HTML 5.

Is it <br>, <br/> or <br />?