Editing Query string (section)

=== Indexed search ===
Before [[form (HTML)|forms]] were added to HTML, browsers rendered the –{{tag|isindex|open}} element as a single-line text-input control. The text entered into this control was sent to the server as a query string addition to a [[GET (HTTP)|GET]] request for the base URL or another URL specified by the {{code|action}} attribute.<ref>{{cite web |title=&lt;isindex&gt; |url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/isindex |website=HTML (HyperText Markup Language) |access-date=2015-11-21 |archive-date=2017-10-19 |archive-url=https://web.archive.org/web/20171019030835/https://developer.mozilla.org/en-US/docs/Web/HTML/Element/isindex |url-status=dead }}</ref> This was intended to allow web servers to use the provided text as query criteria so they could return a list of matching pages.<ref>{{cite web |title=HTML/Elements/isindex |url=https://www.w3.org/wiki/HTML/Elements/isindex |website=W3C Wiki |access-date=2020-03-20 |archive-date=2021-06-22 |archive-url=https://web.archive.org/web/20210622024419/https://www.w3.org/wiki/HTML/Elements/isindex |url-status=dead }}</ref>

When the text input into the indexed search control is submitted, it is encoded as a query string as follows:
{{quote|1=<code>argument1+argument2+argument3...</code>}}
* The query string is composed of a series of arguments by parsing the text into words at the spaces.
* The series is separated by the [[plus sign]], '<code>+</code>'.

Though the {{tag|isindex|open}} element is deprecated and most browsers no longer support or render it, there are still some vestiges of indexed search in existence. For example, this is the source of the special handling of [[plus sign]], '<code>+</code>' within browser URL percent encoding (which today, with the deprecation of indexed search, is all but redundant with <code>%20</code>). Also some web servers supporting [[Common Gateway Interface|CGI]] (e.g., [[Apache HTTP Server|Apache]]) will process the query string into command line arguments if it does not contain an [[equals sign]], '<code>=</code>' (as per section 4.4 of CGI 1.1). Some CGI scripts still depend on and use this historic behavior for URLs embedded in HTML.