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Query String Parser

Parse a URL query string into JSON and convert JSON back into a query string.

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About this tool

Query String Parser is a free, in-browser developer tool that turns a URL query string into a formatted JSON object and rebuilds a query string from JSON. It runs on the browser's native URLSearchParams and URL parsing, so results match what the platform itself produces.

Paste a raw query string, a fragment starting with ?, or a whole URL — only the part after the ? is read, which makes it handy for inspecting analytics links, API request URLs, or OAuth redirects. Keys that appear more than once collapse into a JSON array, + and percent-encoded sequences are decoded to their real characters, and the JSON is pretty-printed with two-space indentation.

Feeding a flat JSON object the other way rebuilds an encoded query string, expanding array values back into repeated keys. Everything runs 100% in the browser: nothing is uploaded, there are no accounts or tracking, and it works offline.

Frequently asked questions

Can I paste a full URL?
Yes. Paste a complete URL and only its query portion — everything after the ? — is parsed into JSON; the scheme, host, path, and hash are ignored.
How are repeated keys handled?
Keys that appear more than once become a JSON array of all their values, and an array value is expanded back into repeated keys when you convert JSON to a query string.
How are spaces and encoded characters handled?
Parsing to JSON decodes + to a space and resolves percent-encoded sequences like %20 to their real characters. Building a query string re-encodes them, so spaces become + and special characters are percent-encoded again.
What JSON can I convert back to a query string?
A flat JSON object. Arrays, primitives, and null are rejected, and each value is converted to a string, so a nested object turns into text rather than more parameters.

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