Query String Builder
Build a properly URL-encoded query string from key/value pairs, with an optional base URL — runs 100% in your browser, nothing is uploaded.
🔒 Query strings are built in your browser — nothing is uploaded.
What this tool does
Query String Builder turns a list of key/value pairs into a correctly URL-encoded query string. Type each parameter name and its value into the rows, add or remove rows as needed, and the encoded output updates live below. Spaces, ampersands, equals signs, plus signs, and other reserved characters are escaped with encodeURIComponent so the result is always safe to paste into a link. Add an optional base URL and the tool joins everything with a ?, or a & when the URL already contains parameters.
How to use it
Optionally paste a base URL like https://example.com/search. Fill in a key and value on each row, using the Add row button for more parameters and the ✕ button to drop one. Rows with an empty key are skipped automatically, and empty values are kept as key=. When the result looks right, press Copy to put the finished query string (or full URL) on your clipboard.
Frequently asked questions
How are special characters handled?
Every key and value is escaped with encodeURIComponent, so spaces become %20, and characters like &, =, +, and # are percent-encoded. Turn on “encode spaces as +” to use the application/x-www-form-urlencoded form style instead, matching what HTML forms and URLSearchParams produce. The output is always a valid query string you can safely paste into a URL.
What happens to empty keys or values?
Rows with an empty key are skipped entirely. A row with a key but an empty value is kept as key= , which is a valid parameter with no value.
Is anything I type uploaded?
No. The query string is built entirely in your browser with JavaScript. Your keys, values, and base URL are never sent to any server.