A query string is the part of a URL that carries extra information to a website in the form of key–value pairs, usually after a question mark.

What a query string is

  • A query string is a section added to the end of a URL to pass data like search terms, filters, or tracking info to the server.
  • It typically starts with ? and contains one or more parameters such as ?search=shoes&color=blue.

Basic structure

  • Each parameter is a key and a value joined with =, for example color=blue.
  • Multiple parameters are separated by &, as in ?category=shoes&size=45&in_stock=true.

Simple example

  • In https://example.com/products?type=shirt&size=medium, the path is /products and everything after ? (type=shirt&size=medium) is the query string.
  • Here, type=shirt and size=medium tell the server which items to show or how to customize the page.

What query strings are used for

  • Passing user input from forms (like search boxes) so the server can return matching results.
  • Controlling page behavior: filters, sorting, pagination, and tracking marketing campaigns or user actions.

Why they matter today

  • Modern sites use query strings heavily for dynamic pages, analytics tags (like campaign IDs), and A/B tests.
  • They also affect SEO and link sharing, so developers try to keep them clean, meaningful, and not overly long.

Information gathered from public forums or data available on the internet and portrayed here.