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How Query Strings Work in URLs
Query strings are the part of a URL that carry parameter values after a question mark. They are widely used for filters, redirects, tracking, search pages, API requests, and many everyday developer workflows.
Published March 6, 2026 · Updated March 16, 2026
What A Query String Does
A query string adds key-value data to a URL. In a URL like ?from=png&to=jpg, the query string carries two separate parameters that can be read by an application, browser, or backend service.
This structure is common in search interfaces, conversion tools, analytics links, redirect targets, pagination, filters, and integrations that need to pass small pieces of data through a URL.
How The Syntax Works
A query string usually starts with a question mark, followed by one or more key=value pairs. Multiple parameters are joined with ampersands, so something like ?page=2&sort=newest includes two separate values.
When values contain spaces or special characters, they are URL-encoded so the link stays valid. That is why query strings and URL encoding often go together in practical web workflows.
Why Parser And Builder Tools Help
A query string parser helps when you want to inspect a link and quickly see each decoded parameter on its own line. This is useful for debugging redirects, tracking links, campaign parameters, and app integrations.
A query string builder is useful in the opposite direction. It lets you start with clean key=value inputs and generate a finished query string without manually encoding every value yourself.