HTML Standard

Links are a conceptual construct, created by a, area, form, and link elements, that represent a connection between two resources, one of which is the current Document. There are three kinds of links in HTML:

For link elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute, as defined for those keywords in the link types section.

Similarly, for a and area elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute as defined for those keywords in the link types section. Unlike link elements, however, a and area elements with an href attribute that either do not have a rel attribute, or whose rel attribute has no keywords that are defined as specifying hyperlinks, must also create a hyperlink. This implied hyperlink has no special meaning (it has no link type) beyond linking the element's node document to the resource given by the element's href attribute.

Similarly, for form elements with a rel attribute, links must be created for the keywords of the rel attribute as defined for those keywords in the link types section. form elements that do not have a rel attribute, or whose rel attribute has no keywords that are defined as specifying hyperlinks, must also create a hyperlink.

A hyperlink can have one or more hyperlink annotations that modify the processing semantics of that hyperlink.

4.6.2 Links created by a and area elements

The href attribute on a and area elements is not required; when those elements do not have href attributes they do not create hyperlinks.

The download attribute, if present, indicates that the author intends the hyperlink to be used for downloading a resource. The attribute may have a value; the value, if any, specifies the default filename that the author recommends for use in labeling the resource in a local file system. There are no restrictions on allowed values, but authors are cautioned that most file systems have limitations with regard to what punctuation is supported in filenames, and user agents are likely to adjust filenames accordingly.

The rel attribute has no default value. If the attribute is omitted or if none of the values in the attribute are recognized by the user agent, then the document has no particular relationship with the destination resource other than there being a hyperlink between the two.

The hreflang attribute on a elements that create hyperlinks, if present, gives the language of the linked resource. It is purely advisory. The value must be a valid BCP 47 language tag. [BCP47] User agents must not consider this attribute authoritative — upon fetching the resource, user agents must use only language information associated with the resource to determine its language, not metadata included in the link to the resource.

The type attribute, if present, gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type string. User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use metadata included in the link to the resource to determine its type.

When an a or area element's activation behavior is invoked, the user agent may allow the user to indicate a preference regarding whether the hyperlink is to be used for navigation or whether the resource it specifies is to be downloaded.

In the absence of a user preference, the default should be navigation if the element has no download attribute, and should be to download the specified resource if it does.

The activation behavior of an a or area element element given an event event is:

If element has no href attribute, then return.
Let hyperlinkSuffix be null.
If element is an a element, and event's target is an img with an ismap attribute specified, then:
1. Let x and y be 0.
2. If event's isTrusted attribute is initialized to true, then set x to the distance in CSS pixels from the left edge of the image to the location of the click, and set y to the distance in CSS pixels from the top edge of the image to the location of the click.
3. If x is negative, set x to 0.
4. If y is negative, set y to 0.
5. Set hyperlinkSuffix to the concatenation of U+003F (?), the value of x expressed as a base-ten integer using ASCII digits, U+002C (,), and the value of y expressed as a base-ten integer using ASCII digits.
Let userInvolvement be event's user navigation involvement.
If the user has expressed a preference to download the hyperlink, then set userInvolvement to "browser UI".

That is, if the user has expressed a specific preference for downloading, this no longer counts as merely "activation".
If element has a download attribute, or if the user has expressed a preference to download the hyperlink, then download the hyperlink created by element with hyperlinkSuffix set to hyperlinkSuffix and userInvolvement set to userInvolvement.
Otherwise, follow the hyperlink created by element with hyperlinkSuffix set to hyperlinkSuffix and userInvolvement set to userInvolvement.

interface mixin HTMLHyperlinkElementUtils { [CEReactions, ReflectSetter] stringifier attribute USVString href; readonly attribute USVString origin; [CEReactions] attribute USVString protocol; [CEReactions] attribute USVString username; [CEReactions] attribute USVString password; [CEReactions] attribute USVString host; [CEReactions] attribute USVString hostname; [CEReactions] attribute USVString port; [CEReactions] attribute USVString pathname; [CEReactions] attribute USVString search; [CEReactions] attribute USVString hash; };

HTML

4.6 Links

4.6.1 Introduction

4.6.2 Links created by `a` and `area` elements

4.6.3 API for `a` and `area` elements

4.6 Links

4.6.1 Introduction

4.6.2 Links created by a and area elements

4.6.3 API for a and area elements

4.6.2 Links created by `a` and `area` elements

4.6.3 API for `a` and `area` elements