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Format, validate, and explore JSON with a live tree view.
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A JSON formatter (also called a JSON beautifier or pretty-printer) takes compact or messy JSON and turns it into readable, indented data. It is one of the most reached-for developer tools — used while inspecting API responses, reading config files, debugging logs, comparing test fixtures, and moving data between frontend and backend code.
JSON is a strict format: keys must be in double quotes, strings must be in double quotes, commas must be in the right place, and every opening { or [ must be closed. A formatter makes that structure visible, and a built-in validator tells you exactly where the syntax breaks if it does.
JSON stands for JavaScript Object Notation. Although it grew out of JavaScript, almost every programming language has built-in support for reading and writing JSON, which is why it has become the default way to exchange structured data on the web.
{} for named fields, arrays use [] for ordered lists, and both can be nested inside each other to any depth.null, object, and array. There is no undefined, no functions, and no comments.Copy the JSON from your API response, log file, or config and paste it on the left. The formatter accepts both minified and partially formatted input.
Two spaces is the most common style; four spaces is also widely used. Pick whichever matches your project's existing style.
If the JSON is valid, the formatted output appears on the right. If it isn't, the error message tells you the line and character where parsing failed.
Use the collapsible tree to fold deeply nested objects and arrays. This is the fastest way to understand the shape of an unfamiliar API response.
Copy the pretty-printed version into your code or docs, or minify it back to a single line for storage and network transport.
The complete set of JSON building blocks. Anything outside this list is not valid JSON. Specification: RFC 8259 and ECMA-404.
| Token | Meaning | Example |
|---|---|---|
{ } | Object — collection of key/value pairs | {"name": "Maya"} |
[ ] | Array — ordered list of values | [1, 2, 3] |
"..." | String — always wrapped in double quotes | "hello" |
| Number | Integer or float, no quotes, no leading + | 42, -3.14 |
true / false | Boolean values, lowercase | true |
null | Empty / missing value | null |
: | Separator between a key and its value | "id": 7 |
, | Separator between items — never trailing | [1, 2, 3] |
{"user":{"id":7,"name":"Maya"},"skills":["HTML","JavaScript"]}{ "user": { "id": 7, "name": "Maya" }, "skills": ["HTML", "JavaScript"]}After formatting, the nested user object and the skills array become much easier to scan. The data is identical — only the whitespace changes.
{ "name": "Coddy", "active": true,}JSON does not allow a trailing comma after the last property. The validator will flag the closing }. This is one of the most common mistakes when copying JavaScript object syntax into JSON.
{ "count": 3, "countText": "3", "enabled": true}3 is a number, "3" is a string, and true is a boolean — three different JSON types. APIs often fail when the shape is right but a value type is wrong.
{ "data": { "orders": [ { "id": 101, "items": [{ "sku": "A", "qty": 2 }] }, { "id": 102, "items": [] } ] }}Use the tree view to collapse data.orders and reveal the shape one level at a time. Nested arrays of objects are the most common pattern in REST responses.
undefined are not valid in JSON, and trailing commas will fail to parse.+, leading zeros (except 0 itself), or be wrapped in quotes if you actually want a number type.null values stay exactly the same. Minifying it back will reproduce the original network-friendly form.undefined are not allowed.package.json, tsconfig.json), package metadata, log lines, browser local storage, and test fixtures.