miji.beA URL parameter (also called a query parameter or query string) is data in "key=value" format appended after the "?" symbol at the end of a URL. For example, in "https://example.com/search?q=short+url&lang=en", q=short+url and lang=en are URL parameters. Multiple parameters are joined with "&".
URL parameters serve three main purposes. First, search and filtering (product searches and category filters on e-commerce sites). Second, tracking (UTM parameters for identifying traffic sources). Third, pagination (specifying a page number such as page=2).
The relationship between short URLs and URL parameters is close. In marketing campaigns, UTM parameters (utm_source, utm_medium, utm_campaign, etc.) are appended to the original URL to track traffic sources, but adding them makes the URL very long. A short URL service converts the lengthy parameterized URL into a compact link that is easy to share on social media and in emails.
From an SEO perspective, URL parameters require careful handling. If the same content is accessible through multiple URLs with different parameters, search engines may treat them as duplicate content. Setting a canonical tag to specify the authoritative URL is the primary way to address this. Google Search Console once offered a "URL Parameters" tool for controlling how parameters were crawled, but it was retired in 2022, so canonical tags and robots directives now do this work.
URL parameters also carry security implications. Parameter values are recorded in browser history and server access logs, so passwords and personal information must never be placed in parameters. Sensitive data should be sent in the body of a POST request.