HTML <base> element

<base> tag defines the default base URL of all links in the web page. It's a void tag, and no closing tag such as </base> is needed. <base> tag is usually placed between <head> ... <head> section.

If the following base tag is placed between <head> ... <head> section, then the followed links will be the same:

<base href="">

<a href="index.php">Default link</a>
<a href="">Default link</a>
<a href="/index.php">Default link</a>

Default link
Default link
Default link