Query String

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In the context of the world wide web, a query string is the part of a URL or web address containing data that does not fit into the conventional, path-like structure of a URL.

It's separated from the other parts of the URL by a question mark ? character.

Consider this URL:


It consists of the following parts:

  • http is the scheme
  • example.com is the host or server
  • /cakes is the path
  • type=chocolate&minimum_available=15 is the query string

Query String Format

Although a query string can contain any characters the browser doesn't treat specially, they'll most often look like the query string above, i.e.,


This format encodes a set of key/value pairs. Here, type and minimum_available are two keys with the values chocolate and 15, respectively.

Storing Dynamic Information

The query string is a common place to place dynamic, user-supplied data. For example, a website might have a "search" feature. Imagine a URL like


which displays some kind of product search form when a user visits it in their browser. The form contains a text search box and a drop-down to limit the search to a specific product category. When the user submits the form, they might be sent a page containing the search results with a URL like


If we changed epson to lexmark, we'd get a different set of search results. Keep in mind this is all hypothetical. These URLs will only do what we describe if there's a web application on the other end expecting these URLS and implementing what we describe.