URL parameters, also known as query parameters or query strings, are optional parts of a URL that pass additional information to a web server.

These parameters are used to modify the behavior of a web page or to send data to a server for processing.

URL parameters follow the main part of the URL and are separated by a question mark (?), with each parameter being a key-value pair separated by an equals sign (=). Multiple parameters can be included in a URL, separated by an ampersand (&).

Here’s the structure of a URL with parameters:

URL parameters are used for various purposes, including:

  • Filtering or sorting content: Parameters can be used to filter or sort results on a web page, such as products in an e-commerce store or articles on a news website.
    Example: https://www.example.com/products?category=electronics&sort=price_asc
  • Pagination: URL parameters can be used to specify the page number or offset for paginated content.
    Example: https://www.example.com/articles?page=2
  • Tracking and analytics: Marketers and analysts often use URL parameters to track the source, medium, or campaign of website traffic.
    Example: https://www.example.com/landing-page?utm_source=google&utm_medium=cpc&utm_campaign=summer_sale
  • Passing data to a server: URL parameters can send data to a server for processing, such as form submissions or API requests.
    Example: https://www.example.com/search?q=keyword&limit=10
  • Maintaining application state: Web applications may use URL parameters to store the current state of the application, allowing users to bookmark or share specific views.
    Example: https://www.example.com/dashboard?view=monthly&date=2023-03

While URL parameters are useful, they can also pose challenges for SEO and web performance. Search engines may interpret URLs with different parameters as separate pages, leading to duplicate content issues.

Long or complex parameter strings can also make URLs less user-friendly and harder to read. To address these issues, web developers can use techniques like canonicalization, URL rewriting, or server-side rendering to optimize URLs and improve the handling of parameters.