Compatibility issues[ edit ] According to the HTTP specification: Various ad hoc limitations on request-line length are found in practice. These facts allow query strings to be used to track users in a manner similar to that provided by HTTP cookies.
Web forms may include fields that are not visible to the user; these fields are included in the query string when the form is submitted This convention is a W3C recommendation.
For example, if you are going to be using a character other than a question mark to start your query string, you need to make use of method 2 below to get your query string to work with. The question mark is used as a separator, and is not part of the query string.
Main article: Percent-encoding Some characters cannot be part of a URL for example, the space and some other characters have a special meaning in a URL: for example, the character can be used to further specify a subsection or fragment of a document.
A link in a web page may have a URL that contains a query string. This method should only be used if the next method produces an incorrect value for some reason, or if you are using a character other than a question mark to begin your query string such as a slash.
Secondly, we have to figure out what kind of output we want from our function. The query string is composed of a series of field-value pairs. If the user arrives at the same web server by two or more independent paths, it will be assigned two different query strings, while the stored cookies are the same.
When the user follows, for example, the first link, the browser requests the page foo.