Input JSON
Output
Tree · Pretty · Minified
Parse and validate JSON, then view it as a collapsible tree, pretty-printed, or minified. Invalid JSON? The parser reports the exact syntax error so you can fix it fast. Runs entirely in your browser.
No installation, no signup. Results in milliseconds.
A JSON parser reads JSON text, checks that it is syntactically valid, and converts it into structured data your program (or this page) can work with. If anything is malformed, the parser stops and reports where the problem is.
A parser interprets JSON into data; a formatter re-indents it; a validator only checks correctness. This tool does all three at once — it validates, reports errors, and offers tree, pretty, and minified output.
JSON is defined by RFC 8259. A parser accepts data only when it follows these rules exactly — the most common reason JSON.parse() throws is one of the mistakes below.
| Rule | Valid | Invalid |
|---|---|---|
| Strings use double quotes | "name" | 'name' |
| Object keys must be quoted | {"a":1} | {a:1} |
| No trailing commas | [1,2] | [1,2,] |
| No comments allowed | {"a":1} | {"a":1} // note |
| Numbers: no leading zeros, no NaN/Infinity | 42, -3.14, 1e5 | 042, NaN |
| Only one top-level value | [{"a":1},{"b":2}] | {"a":1}{"b":2} |
When a parse fails, the message points at the cause. These are the errors developers hit most often:
| Error message | Cause | Fix |
|---|---|---|
Unexpected token o in JSON | You passed an object, not a JSON string | Stringify it first, or paste the raw text |
Unexpected end of JSON input | The payload is truncated or empty | Confirm the full response was received |
Unexpected non-whitespace character after JSON | Two roots, or trailing content | Wrap the values in an array |
Bad control character in string literal | A raw newline or tab inside a string | Escape them as \n / \t |
Expected property name… | A trailing comma or unquoted key | Remove the comma; quote the key |
In JavaScript, JSON.parse(text) returns a value and throws a SyntaxError on malformed input, so wrap it in try/catch. In Python, json.loads(text) does the same and raises JSONDecodeError. This parser mirrors that behaviour in the browser: it validates as you type and reports the exact failure point, then lets you switch to the tree view or grab pretty-printed or minified output from the same parse — no install, nothing uploaded.
When JSON fails to parse, the message tells you exactly what to fix. Here is how to read it.
Paste JSON with a mistake and the parser stops at the first problem and reports it. The example above has a trailing comma after "b" and another after the closing ]; strict JSON allows neither, so parsing fails with the position of the offending token. Jump to that position, remove the stray commas, and it parses cleanly into the tree, pretty, and minified views.
Most parse failures come from a short list of causes. This table maps the errors you will actually see to their fix.
| Error | Likely cause | Fix |
|---|---|---|
| Unexpected token } / ] | Trailing comma before the closing brace or bracket. | Remove the comma after the last item. |
| Unexpected end of JSON input | A truncated payload or a missing closing } or ]. | Add the missing bracket, or re-copy the full response. |
| Unexpected token ' | Single quotes used for strings or keys. | Switch to double quotes — JSON requires them. |
| Expected property name | An unquoted key, or a comma with no following key. | Quote every key and drop trailing commas. |
| Bad control character in string | A raw newline or tab inside a string. | Escape it as \n or \t. |
For a deeper walkthrough of the most common one, see our guide on fixing "Unexpected token" JSON errors.
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