What is JSON Stringify Online?
JSON Stringify Online is a free tool that runs JSON.stringify() in your browser — no code editor, no console, no setup. Paste any JavaScript object, array, or value, click Stringify, and you instantly get the JSON string you can copy into your code or download as a file. Everything is processed locally; your data is never sent to a server.
Think of it as calling JSON.stringify(value, null, 2) in the browser DevTools console — except with a clean UI, configurable indentation, sort-keys support, and a one-click copy button.
JSON.stringify() Syntax and Parameters
The full signature of the built-in JavaScript function is:
JSON.stringify(value, replacer, space)
- value — The JavaScript value to serialise (object, array, string, number, boolean, or null).
- replacer — (Optional) A function or array that filters which properties are included. Pass
nullto include everything. This tool usesnullby default and a sorted-key array when Sort Keys is enabled. - space — (Optional) A number (0–10) or string (e.g.,
"\t") that adds indentation. Omit or use 0 for compact JSON; use 2 or 4 for human-readable pretty-print.
JSON.stringify() with Pretty Print (Indentation)
The most common real-world usage of JSON.stringify() is with the third space argument for readable output:
JSON.stringify(obj, null, 2)— 2-space indent (most popular)JSON.stringify(obj, null, 4)— 4-space indentJSON.stringify(obj, null, "\t")— tab indentJSON.stringify(obj)— compact, no whitespace
On this JSON stringify online tool, use the Indent selector in the toolbar to switch between these modes visually without writing any code.
JSON.stringify vs JSON.parse — What's the Difference?
These two methods are exact opposites:
JSON.stringify(obj)— Serialises (encodes) a JavaScript value into a JSON string. Use it when you need to send data over a network, save to localStorage, or write to a file.JSON.parse(str)— Deserialises (decodes) a JSON string back into a JavaScript value. Use it when you receive JSON from an API or read it from storage.
A common pattern combining both: JSON.parse(JSON.stringify(obj)) creates a deep clone of a plain object.
JS String Literal vs Pretty JSON — Which Should I Copy?
This tool has two output modes:
- JS String Literal — The actual string that
JSON.stringify()returns in JavaScript. It is compact, wrapped in double quotes, and has internal double quotes escaped as\". This is what you paste directly into JavaScript source code as a string value. - JSON Content — The same data formatted with indentation and syntax highlighting. Easier to read, and suitable for saving as a
.jsonfile or pasting into an API body field.
Common Use Cases for JSON Stringify Online
- API Payloads — Serialise a request body before calling
fetch()orXMLHttpRequest. - LocalStorage & SessionStorage — Browsers only store strings; stringify objects before saving and parse them on retrieval.
- Configuration Files — Generate
package.json,tsconfig.json, or custom config files programmatically. - Debugging & Logging — Pretty-print a complex object to a console or log file with
JSON.stringify(obj, null, 2). - Deep Clone — Quick deep-clone for plain objects:
const clone = JSON.parse(JSON.stringify(obj)).
Special Cases: What JSON.stringify() Skips or Transforms
- undefined values — Object properties with an
undefinedvalue are silently omitted. In arrays,undefinedelements becomenull. - Functions and Symbols — Properties whose values are functions or Symbols are dropped entirely.
- Date objects — Converted to their ISO 8601 string representation (e.g.,
"2024-01-01T00:00:00.000Z"). - Circular references — Throw a
TypeError: cyclic object value. Resolve them with a custom replacer or a library likeflatted. - BigInt — Throws a
TypeError: Do not know how to serialize a BigInt. Convert to string first:bigIntValue.toString().
Why Use This JSON Stringify Online Tool?
Unlike opening browser DevTools or a code editor, this tool requires zero setup. Paste your data, pick your indent and sort options, toggle between JS String Literal and JSON Content output, and copy or download instantly. It runs entirely in your browser — safe for API keys, passwords, and confidential configuration — and works on any device with a modern browser.