About JSON → Query String

Serialize a flat JSON object into a URL query string. Part of the DevTools Surf developer suite. Browse more tools in the Converters collection.

Use Cases

• API developers converting JSON payloads to GET request params
• Frontend devs serializing filter state into shareable URLs
• Test automation engineers building parameterized test URLs
• Backend devs migrating POST body parameters to query strings

Tips

• Paste a flat JSON object to instantly get a query string
• Nested objects are not supported — flatten them first
• Output is URL-encoded and ready for direct use in requests

Fun Facts

• JSON was formalized by Douglas Crockford in 2001 and standardized as ECMA-404 in 2013, despite being based on a subset of JavaScript syntax from 1999.
• The application/x-www-form-urlencoded MIME type used for query strings is the default encoding for HTML forms and dates back to HTML 2.0 (RFC 1866, 1995).
• The qs npm library, which handles nested JSON-to-query-string conversion, receives over 60 million weekly downloads — one of npm's most depended-upon packages.

FAQ

How are nested objects encoded?

Bracket notation: `user[name]=alice&user[age]=30`. Alternative styles (dot notation, JSON-encoded values) are toggleable.

What about arrays?

Three modes: repeated key (`tag=a&tag=b`), bracket with index (`tag[0]=a&tag[1]=b`), or comma-separated (`tag=a,b`). Default matches standard URL encoding.

Are values URL-encoded?

Yes — automatically percent-encoded. Spaces become `%20` (default) or `+` (form mode).

Does the output start with `?`?

Toggle — include the leading `?` for appending to a base URL, or omit it when the context already has one.