JSON Formatter & Validator

How to use JSON Formatter

1. Paste raw or minified JSON into the box.
2. Click "Format & validate".
3. Valid JSON is reformatted with clean indentation; invalid JSON shows a clear error.
4. Click "Copy output" to copy the result.

Fixing invalid JSON

When your JSON doesn't parse, QuickTiny explains why in plain English alongside the raw parser error — for example, pointing out a trailing comma, a single quote where a double quote belongs, or an unquoted key. If the problem is one of a handful of common, unambiguous issues (trailing commas, single-quoted strings, unquoted keys, a ```json markdown code fence still wrapped around the output, explanatory text before or after the JSON, or several JSON objects pasted back to back — the kind that show up constantly in output copied from ChatGPT, Claude, or hand-edited config files), click "Try to fix common issues" and QuickTiny will correct it automatically and tell you exactly what it changed. If the JSON is incomplete — missing a closing bracket or ending mid-string because a response got cut off mid-generation — QuickTiny will say so instead of guessing at what's missing, since there's no safe way to reconstruct content that was never there. Severely truncated JSON isn't something any automatic fixer can safely repair.

Example: fixing JSON copied from ChatGPT or Claude

AI chat responses commonly introduce the same handful of issues: a trailing comma left in after editing a list, a stray single-quoted string, or an unquoted key typed out of habit. Here's a realistic example with all three, pasted as-is:

{
  "name": "Alex",
  "role": 'admin',
  city: "Austin",
  "tags": ["a", "b",]
}

{
  "name": "Alex",
  "role": "admin",
  "city": "Austin",
  "tags": [
    "a",
    "b"
  ]
}

QuickTiny reports exactly what changed: converted 1 single-quoted string to double quotes, removed 1 trailing comma, quoted 1 unquoted key — the same three fixes, whether the JSON came from ChatGPT, Claude, or was typed by hand.

Common JSON error messages, explained

Landed here searching for one of these exact messages? Here's what each one means and how to fix it — paste your JSON into the tool above and click "Try to fix common issues" instead of fixing it by hand.

"Expected property name or '}' in JSON at position 1"

This fires when the very first thing inside your opening { isn't a valid double-quoted key — almost always an unquoted key or a single-quoted key. Position 1 (column 2) is the character right after {, exactly where a key should start.

{name: "Alex"}

{"name": "Alex"}

A single-quoted key in that same spot — {'name': "Alex"} — throws the identical error. Both are exactly what "Try to fix common issues" corrects automatically.

"Unexpected token ' in JSON"

The sibling error to the one above, but for a single-quoted value instead of a key — JSON requires double quotes for strings everywhere, not just in keys. V8 (Chrome, Node.js) echoes back the start of your actual input in the message, so the quoted part will match whatever you pasted rather than the example above.

{"role": 'admin'}

{"role": "admin"}

Python: "Expecting property name enclosed in double quotes"

Python's json module uses this one message for all three causes above — an unquoted key, a single-quoted key, or a trailing comma — where JavaScript reports them as separate errors. The fix is the same regardless of which language eventually parses it: valid double-quoted keys and no trailing commas.

{name: 'Alex'}

{"name": "Alex"}

QuickTiny's formatter runs in your browser, not Python — but the corrected JSON it produces is valid everywhere. Paste your broken JSON above, fix it once, then copy the result into your Python code. Nothing you paste is uploaded or logged.

"Unexpected token '<'" (getting HTML instead of JSON)

This means whatever you're parsing isn't JSON at all — it's HTML, almost always because an API call returned an error page (a 404 or 500 page, or a login redirect) instead of the JSON response you expected. The < at the very start is the opening angle bracket of <!DOCTYPE html> or <html>. Pasting the response into this tool won't fix it — the real fix is checking the actual HTTP response (your browser's Network tab, or logging the raw response body before calling .json()) to see what your server or API actually sent back.

"Unexpected end of JSON input"

The JSON stopped in the middle of something — usually a response that got cut off (a network request that didn't finish, or AI chat output that hit a length limit mid-generation), or simply an empty string being parsed. Unlike a trailing comma or single quote, there's no safe way to guess what content was supposed to come next, so QuickTiny will tell you the JSON is incomplete rather than attempt a fix — you'll need the complete response, not a patch on this one.

Python: "Expecting value", "Expecting ',' delimiter", and "Extra data"

These three Python messages cover different broken-JSON situations than the single-quote/unquoted-key error above:

• Expecting value — the input is empty, a key's value is missing entirely (e.g. {"a": }), or the input isn't JSON at all.
• Expecting ',' delimiter — two key-value pairs sit next to each other with no comma between them, like {"a": 1 "b": 2}.
• Extra data — there's valid JSON followed by more content after it — commonly two JSON objects concatenated together, like {"a": 1}{"b": 2}.

{"a": 1 "b": 2}

{"a": 1, "b": 2}

Paste any of these into the tool above and you'll see JavaScript's version of the same complaint, worded differently but pointing at the identical problem. A missing comma between two values still needs a manual edit. Concatenated JSON objects are different — "Try to fix common issues" now detects two or more complete JSON objects pasted back to back and offers to wrap them in an array instead of requiring you to split them by hand.

Key benefits

• Plain-English explanations alongside the raw parser error.
• One-click automatic fix for trailing commas, single quotes, unquoted keys, markdown code fences, surrounding explanatory text, and concatenated JSON objects.
• Two-space indentation for readable, diff-friendly JSON.
• Runs locally — your JSON is never sent to a server, logged, or stored anywhere.
• One-click copy of the formatted result.

Privacy

JSON Formatter runs entirely in your browser using local JavaScript. Your JSON is processed on your own device and is never uploaded, logged, or stored by QuickTiny — including when using the automatic fix. There is no history feature and no record of what you've pasted.

Frequently asked questions