Query string

A query string is a part of a uniform resource locator (URL) that assigns values to specified parameters.

A query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML document, choosing the appearance of a page, or jumping to positions in multimedia content.

[1][2] Web frameworks may provide methods for parsing multiple parameters in the query string, separated by some delimiter.

The same encoding is used by default when the submission method is POST, but the result is submitted as the HTTP request body rather than being included in a modified URL.

[8] Before forms were added to HTML, browsers rendered the – element as a single-line text-input control.

[9] This was intended to allow web servers to use the provided text as query criteria so they could return a list of matching pages.

For example, this is the source of the special handling of plus sign, '+' within browser URL percent encoding (which today, with the deprecation of indexed search, is all but redundant with %20).

The following is a brief summary of the algorithm: The octet corresponding to the tilde ("~") is permitted in query strings by RFC3986 but required to be percent-encoded in HTML forms to "%7E".

If a form is embedded in an HTML page as follows: and the user inserts the strings "this is a field" and "was it clear (already)?"

These facts allow query strings to be used to track users in a manner similar to that provided by HTTP cookies.

The limit is configurable on Apache2 using the LimitRequestBody directive, which specifies the number of bytes from 0 (meaning unlimited) to 2147483647 (2 GB) that are allowed in a request body.