Which tag is placed in the head section to define the base URL?

The <base> tag is specifically designed to define a base URL for relative URLs in a document. When you include the <base> tag within the head section of an HTML document, it establishes a reference point for all relative links (such as those in <a>, <img>, and others) throughout that document. This allows the browser to resolve the relative URLs correctly by appending them to the base URL specified in the <base> tag.

For example, if you set the <base> tag to point to "https://www.example.com/", then any relative link, like "page.html", will be interpreted as "https://www.example.com/page.html". This is particularly advantageous in large websites or when links need to be dynamically generated, ensuring consistency and accuracy in navigation.

The other tags mentioned have different purposes: the <meta> tag is used for metadata about the HTML document; the <link> tag typically links external resources like stylesheets; and the <title> tag specifies the title of the document, which appears in the browser's title bar or tab. Each of these tags contributes to different aspects of HTML and document structure but does not serve the function of defining a base URL.