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Query string to JSON

Parse a URL query string into JSON and build one back. Repeated keys become an array, tag[]= and filtre[prix]= expand into arrays and objects, + is a space and %C3%A9 is é.

Related tools

All JSON, XML & formats tools →
JSON to query stringTurn a flat JSON object into a URL query string.Query String BuilderBuild a URL query string from key/value rows with correct percent-encoding, array syntax options and a UTM preset — or parse an existing URL back into rows.JSON String Escape / UnescapeTurn raw text into a JSON-safe string and back, with control characters, \uXXXX, emoji surrogate pairs and lone surrogates handled exactly like JSON.stringify.CSV to JSON converterParse CSV text (with header row) into a JSON array of objects, handling quoted fields. Drop a file in rather than pasting it — it is read in your browser and never uploaded.JSON comment removerStrip // and /* */ comments from JSONC to make it valid JSON. Drop a file in rather than pasting it — it is read in your browser and never uploaded.JSON flattenerFlatten a nested JSON object into one level of path keys — and put it back together again. Arrays are indexed as user.roles[0] or user.roles.0, values keep their type, and an empty object stays visible as {}. Takes a whole file, so a long log does not have to go through the clipboard.JSON formatterFormat, beautify or minify JSON — with instant validation.JSON keys extractorList all the keys of a JSON object as dot-notation paths. Works on a pasted block or on a file you drop in.

Query string to JSON is free to use as often as you like, directly from this page. It sits under JSON, XML & formats in our catalogue, alongside JSON to query string and Query String Builder.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Query string to JSON do?

Parse a URL query string into JSON and build one back. Repeated keys become an array, tag[]= and filtre[prix]= expand into arrays and objects, + is a space and %C3%A9 is é.

When would I actually use this?

Making a machine-generated blob readable, finding the character where a parse fails, and shrinking a file before it ships.

What is the most common mistake?

Assuming valid means correct. A document can parse cleanly and still have the wrong shape for whatever will read it — validation checks the syntax, not the schema.

How is Query string to JSON different from JSON to query string?

They sit next to each other but answer different questions: JSON to query string is the one to open when you need it to turn a flat JSON object into a URL query string. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Query String Builder is the closest one after this: Build a URL query string from key/value rows with correct percent-encoding, array syntax options and a UTM preset — or parse an existing URL back into rows.

What else is worth having open alongside it?

JSON String Escape / Unescape and CSV to JSON converter — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Parsing and serialisation follow each format's specification. Key order and whitespace are not semantically meaningful in JSON or YAML, so a reformatted document is equivalent even when the bytes differ.

Further reading

All guides →
GuideURL Encoding Explained: Percent-Encoding and Where It BitesPercent-encoding is decided per URL component, which is the whole source of the confusion. A slash is legal in a path and must be escaped in a query value; a space is %20 in a path and may be + in a form body. Here are the exact RFC 3986 sets, the three JavaScript functions that disagree, and the traps.ExplainerEscaping a String for JSON: Three Characters Are Mandatory, and One Is a TrapRFC 8259 requires exactly three things to be escaped inside a JSON string. Everything else is optional. The one that actually breaks pipelines is a lone surrogate — legal in JSON text, impossible in UTF-8, and silently replaced the moment your data is written out.ExplainerJSON to CSV When the Structure Is Nested: Why There Is No Right AnswerThe same two orders come out as five columns from one converter and ten from another, and neither is wrong. Dotted paths, arrays of scalars, arrays of objects and records with different keys — four decisions, made for you, usually silently.ExplainerXML to JSON: Attributes, Repetition, and the Single-Element Array TrapTwo documents that differ only in how many children exist produce two different JSON shapes, and no converter can tell them apart without a schema. Plus what this one really does with attributes, mixed content and whitespace — and the one thing it still cannot record.ExplainerCSV to JSON: The Five Cases That Break Every ConverterQuoted delimiters, embedded newlines, ambiguous types, duplicate headers and encoding. Each one was run through the converter and the exact output is printed here — including the two cases it does not rescue.ComparisonJSON vs XML: What's the Difference?JSON and XML both store structured data as text, but they trade off differently. Here's how each looks, where each wins, and how to choose.