Query String Builder converts a JSON object into a URL query string. Enter your parameters as a JSON object and get back the key=value&key=value format ready to append to any URL. All values are automatically percent-encoded so special characters and spaces do not break the URL.
URLs can only contain certain characters directly. Spaces, &, =, and other special characters must be percent-encoded before they appear in a query string. The builder takes each JSON key and value, runs them through encodeURIComponent(), and joins the pairs with = between key and value and & between pairs. JSON arrays expand into repeated parameters with the same key.
Arrays are expanded into repeated parameters. For example, {"id": [1, 2]} produces id=1&id=2 in the query string. This matches the standard convention used by most web frameworks including Express, Django, and Rails for handling array-valued parameters.
Yes. All keys and values are run through encodeURIComponent() before being included in the output. Spaces become %20, & becomes %26, = becomes %3D, and so on. The resulting query string is safe to use in any URL.
The output does not include the leading ? — just the raw parameter string. Add ? before it when appending to a base URL, for example: https://example.com/search?q=hello&page=1
Flat JSON objects with string and number values work directly. Nested objects are serialized using bracket notation (user[name]=John) which frameworks like Laravel, Express with qs, and Python's urllib.parse handle automatically.
No. The serialization runs entirely in your browser. Your JSON data never leaves your device.
Yes, completely free with no account required.
Tool workspace
Free Query String Builder online — instantly convert a JSON object into a perfectly formatted, URL-encoded query string for REST APIs and GET requests. No login.
Output
Input
{"q": "shoes sale", "filters": ["red", "blue"]}Output
q=shoes%20sale&filters=red&filters=blue