<base>: The Document Base URL element
Baseline Widely available *
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
* Some parts of this feature may have varying levels of support.
The<base>HTML element specifies the base URL to use for allrelative URLs in a document. There can be only one<base> element in a document.
A document's used base URL can be accessed by scripts withNode.baseURI. If the document has no<base> elements, thenbaseURI defaults tolocation.href.
Attributes
This element's attributes include theglobal attributes.
Warning:A<base> element must have anhref attribute, atarget attribute, or both.If at least one of these attributes are specified, the<base> elementmust come before other elements with attribute values that are URLs, such as a<link>'shref attribute.
hrefThe base URL to be used throughout the document for relative URLs.Absolute and relative URLs are allowed.
data:and#"#target">targetAkeyword orauthor-defined name of the defaultbrowsing context to show the results of navigation from
<a>,<area>, or<form>elements without explicittargetattributes. The following keywords have special meanings:_self(default): Show the result in the current browsing context._blank: Show the result in a new, unnamed browsing context._parent: Show the result in the parent browsing context of the current one, if the current page is inside a frame. If there is no parent, acts the same as_self._top: Show the result in the topmost browsing context (the browsing context that is an ancestor of the current one and has no parent). If there is no parent, acts the same as_self.
Usage notes
Multiple <base> elements
If multiple<base> elements are used, only the firsthref and firsttarget are obeyed — all others are ignored.
In-page anchors
Links pointing to a fragment in the document — e.g.,<a href="#some-id"> — are resolved with the<base>, triggering an HTTP request to the base URL with the fragment attached.
For example, given<base href="https://example.com/"> and this link:<a href="#anchor">To anchor</a>. The link points tohttps://example.com/#anchor.
target may not contain ASCII newline, tab, or <
If thetarget attribute contains an ASCII newline, tab, or the< character, the value is reset to_blank.This is to prevent dangling markup injection attacks, a script-less attack in which an unclosedtarget attribute is injected into the page so that any text that follows is captured until the browser reaches a character that closes the attribute.
Open Graph
Open Graph tags do not acknowledge<base>, and should always have full absolute URLs. For example:
<meta property="og:image" content="https://example.com/thumbnail.jpg" />Examples
<base href="https://www.example.com/" /><base /><base href="https://example.com/" />Technical summary
| Content categories | Metadata content. |
|---|---|
| Permitted content | None; it is avoid element. |
| Tag omission | Must have a start tag and must not have an end tag. |
| Permitted parents | A<head> that doesn't contain another<base> element. |
| Implicit ARIA role | No corresponding role |
| Permitted ARIA roles | Norole permitted |
| DOM interface | HTMLBaseElement |
Specifications
| Specification |
|---|
| HTML # the-base-element |