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<isindex>

Obsolete
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

<isindex> is an obsolete HTML element that puts a text field in a page for querying the document. <isindex> was providing a single line text input for entering a query string. When sent, the server would return a list of pages matching the query. Its supports depended on both the browser and the server to react to the query.

<isindex> is deprecated as of HTML 4.01, because the same behaviour can be achieved with an HTML form. All major browsers have now removed <isindex>, and it is has been classified as a non-conforming feature in the WHATWG HTML living standard.

Attributes

Like all other HTML elements, this element accepts the global attributes.

prompt: This attribute adds its value as a prompt for text field.
action: This attribute can be used to send the query to a different URL. Action is not defined by W3C.

Example

<head>
  <isindex prompt="Search Document... " />
</head>

History

On June 1992, Dan Connolly would prefer a different anchor type instead of isindex.

On November 1992, indexes as links rather than documents started by Dan Connolly who is pushing the idea that indexes are more links than documents. In this thread, different type of solutions are proposed. The question of forms for making queries is mentioned in reference to Dynatext browser: "The browser displays toggle buttons, text fields etc. The user fills in the fields, clicks OK, and the query results come up in the table of contents window."

A thread about isindex in November 1992, Kevin Hoadley questioned the need for an isindex element and proposed to drop it. He proposed to have instead an input element (idea supported by Steve Putz). Tim Berners-Lee explains the purpose of isindex resulting in aggregated search results. Kevin replies that he doesn't like the boolean nature of isindex and would prefer a system where everything is searchable and proposes to extend the current WWW Framework with a specific httpd configuration and defined that some URIs mapping create search queries.

In 2016, it has been proposed to remove isindex from the specification.

HTML Reference

HTML5 classifies it as a non-conforming feature.
ISINDEX element deprecated in HTML 4.01
ISINDEX in HTML 3.2
ISINDEX in HTML 2.0 as well the description of the behavior in Queries and Indexes (HTML 2.0)
ISINDEX in HTML+

Browser compatibility

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	No	No	No	No	No	No
`action`	No	No	No	No	No	No
`prompt`	No	No	No	No	No	No