JSON Formatter

How to use it

1. Paste your JSON, or drop a .json/.txt file onto the input pane. The formatted result appears immediately — there is no button to press for typical inputs.
2. Pick an indentation: 2 spaces (the default), 4 spaces, tabs, or compact — compact strips every inter-token space, the same output a minifier produces.
3. Leave “Preserve big numbers” on unless you specifically want JavaScript's native number behavior. Off, integers beyond 2⁵³ silently round.
4. If the input is invalid, the error tells you the line, column, and probable cause, with a code frame pointing at the exact character. Your input is never modified.
5. Use Copy for the raw string, Download for a .json file (LF or CRLF line endings), or Share to put the whole tool state into a link.

Paste JSON — or drop a file up to 50 MB — and the formatted result appears as you type. Everything runs on this device: nothing you paste is uploaded. One invariant governs this page: the formatter changes whitespace only — never key order, never values. Numbers longer than JavaScript can represent are preserved digit-for-digit, which is where most online formatters quietly corrupt your data.

Examples

{"id":42,"name":"café ☕","tags":["a","b"],"nested":{"ok":true,"n":null}}

{
  "id": 42,
  "name": "café ☕",
  "tags": [
    "a",
    "b"
  ],
  "nested": {
    "ok": true,
    "n": null
  }
}

{"total": 9007199254740993}

{
  "total": 9007199254740993
}

{
  "id": 42,
  "name": "café ☕",
  "tags": [
    "a",
    "b"
  ],
  "nested": {
    "ok": true,
    "n": null
  }
}

{"id":42,"name":"café ☕","tags":["a","b"],"nested":{"ok":true,"n":null}}

Every example on this page is executed against the same engine that powers the tool, on every build.

Common errors

Unexpected '}' at line 12, column 3 — probable cause: trailing comma after the last property.

JSON forbids a comma after the final property or element. Delete the comma before the closing bracket — or paste the payload into a JSON5-tolerant editor if it was never meant to be strict JSON.

Unexpected "'" at line 1, column 2 — probable cause: single-quoted strings are JSON5, not JSON; use double quotes.

Every string in JSON — keys and values — must use double quotes. Single quotes usually arrive from JavaScript object literals or Python dict dumps.

Unexpected end of input at line 1, column 6 — probable cause: the document is incomplete or truncated.

The parser ran out of characters mid-value: usually a clipped log line, a truncated API response, or a copy that missed the closing brace.

Unterminated string at line 1, column 7 — probable cause: missing closing quote.

A string opened but never closed — usually a quote character inside the value that should have been escaped as \", or a copy that cut off mid-string.

Unexpected '{' at line 2, column 1 — probable cause: multiple JSON documents; this looks like NDJSON / JSON Lines.

One JSON document per file is the rule. Line-delimited JSON (NDJSON) is a different format in which every line is its own document — common in logs and LLM fine-tune datasets.