Query String Parser guide
Decode URL query parameters, preserve repeated keys, inspect JSON, and rebuild a consistently encoded query string.
What this tool does
The Query String Parser accepts either a complete URL or text beginning with an optional question mark. It isolates the portion after ? and before #, then applies the browser's standard URLSearchParams behavior. Percent-encoded bytes are decoded as text, and plus signs in the query are interpreted as spaces.
Repeated keys are preserved as multiple values instead of being silently reduced to the first or last value. The result groups values under each decoded key, displays empty values explicitly, and offers JSON output. The rebuilt query appends every grouped value and applies standard form-style percent encoding.
Parsing and rebuilding are not necessarily byte-for-byte reversible. Spaces may be emitted as +, percent-escape letter case can change, and parameter grouping can change the original interleaving of repeated keys. Those differences normally represent equivalent query data, but systems that sign the exact raw URL may require the untouched source string.
How to use it
- Paste a complete URL or query string.
- Select Parse query string.
- Review decoded keys, repeated values, and empty values.
- Copy JSON for debugging or structured inspection.
- Copy the rebuilt query only when normalized encoding is acceptable.
Never paste live passwords, private API keys, session tokens, authorization codes, or signed links into tools unnecessarily. Although processing is local, secrets can still remain in clipboard history, browser form restoration, screenshots, logs, or the surrounding device environment.
Benefits
- Accepts full URLs and standalone queries
- Decodes standard percent encoding
- Retains repeated keys as ordered values
- Produces readable JSON and a normalized query
- Keeps query processing on the device
Correct interpretation and safety
A decoded value is not automatically safe HTML, a safe database value, or a valid application instruction. Use context-appropriate validation and output encoding before passing values to another system. The parser does not fetch the supplied URL, follow redirects, verify a domain, or check whether a link is malicious.
Fragments beginning with # are excluded because they are not part of the query string. Query parameters without an equals sign are interpreted as keys with empty values.
Security notice: Treat parsed URLs and values as untrusted input and avoid exposing authentication material.