Query String to JSON Converter

How to use the query string to json converter

1. Paste your query string or full URL into the text area.
2. Adjust the indent size if you prefer compact or expanded output.
3. The JSON result updates live as you type.
4. Copy the output for use in code, API testing or configuration files.

How query string parsing works

A query string follows the question mark in a URL and contains key-value pairs separated by ampersands. Each pair uses an equals sign to join the key and value. Converting a query string to JSON means splitting on those delimiters, decoding any percent-encoded characters and building a structured object.

For example, the input name=Alice&age=30 splits into two pairs. After decoding, the resulting JSON is {"name": "Alice", "age": "30"}. Note that all values remain strings because query strings carry no type information. If you need numbers or booleans, parse them after conversion using your language of choice.

The algorithm first strips any URL scheme, host, path or fragment so you can paste a complete address without manually isolating the parameters. It then splits the remaining string on every ampersand, ignoring empty segments caused by trailing or doubled ampersands. Each segment is split at the first equals sign only, which allows values to contain literal equals signs once decoded.

Handling repeated keys

URLs often repeat the same parameter name, such as tag=js&tag=web&tag=api. When converting a query string to JSON, these repeated keys are grouped into an array. The output becomes {"tag": ["js", "web", "api"]}.

If a key appears only once, its value stays a plain string rather than a single-element array. This matches the behaviour of Python's urllib.parse.parse_qs when configured to flatten single values, and keeps the JSON output clean for typical API payloads.

This design choice avoids unnecessary nesting. A search endpoint expecting ?q=test usually wants {"q": "test"}, not {"q": ["test"]}. However, if your downstream system always expects arrays, you can wrap single values programmatically after the conversion step.

Percent-encoding and plus signs

Characters outside the unreserved set must be percent-encoded in URLs. A space can appear as %20 or as a plus sign (+). Both forms are decoded back to a literal space during conversion. Other common encodings include %26 for an ampersand and %3D for an equals sign.

The converter applies standard URI decoding to every key and value. Malformed sequences like a lone percent sign at the end of the string will produce an error rather than silently corrupting the data. This strict approach prevents subtle bugs where partial decoding leaves garbage characters inside your JSON payload.

The plus-as-space rule comes from the application/x-www-form-urlencoded media type defined in the HTML specification. While RFC 3986 treats plus as a literal character in generic URIs, web forms and most server frameworks decode it as a space. This tool follows the web form convention because that is what developers expect when they parse query parameters from HTTP requests.

Common reference patterns

The table above covers the most frequent edge cases. Bare keys without an equals sign map to empty strings. Empty values after an equals sign also map to empty strings. Plus signs become spaces, and percent-encoded slashes decode normally.

Related format conversions

Once you have converted a query string to JSON, you might need to transform that data further. Tools like TOML to JSON, INI to JSON and ENV to JSON handle other configuration formats. For newline-delimited data, see NDJSON to JSON. If your source is tab-separated instead of URL-encoded, TSV to JSON provides the equivalent transformation.

Many backend systems accept configuration through environment variables or flat files but expose APIs over HTTP. Being able to move fluidly between query strings, JSON objects and configuration formats saves time when debugging request pipelines or migrating settings between services.

Worked examples