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JSON Formatter

Format and validate JSON in one pass: paste raw API output and get a properly indented, line-numbered tree you can actually read — with syntax errors flagged the moment they appear.

InputJSON
Output
Input: 0 lines · 0 charsOutput: 0 lines · 0 chars Processed locally in your browser

What is a JSON formatter?

A JSON formatter takes JSON in whatever shape you paste it — minified onto one line, irregularly spaced, or hand-edited — and rewrites it with predictable indentation so the structure is obvious. Objects, arrays and their nesting line up vertically, which turns an unreadable blob into something you can scan top to bottom.

The key difference from a plain pretty-printer is that this tool parses before it formats. Your text is run through JSON.parse() into a real value and re-serialised with JSON.stringify(value, null, 4). If the parse fails, the JSON has a genuine syntax error and you get told about it — so formatting and validation happen together in a single step.

Everything is computed locally in your browser. API responses, config files, webhook payloads and anything carrying tokens or keys can be pasted safely, because the text never leaves your device.

How to format JSON

  1. 1

    Paste your JSON

    Drop raw, minified or messy JSON into the input pane — or upload a .json file.

  2. 2

    Watch it format live

    Formatting runs as you type, so the indented result appears in the right pane immediately.

  3. 3

    Read any error

    If the JSON won't parse, an error message points at the problem so you can fix it before relying on the data.

  4. 4

    Copy or download

    Grab the clean output with the copy button or save it as a .json file.

Why developers reach for it

Format and validate at once

Because the input is parsed first, a clean result also proves the JSON is well-formed — no separate validator needed.

Read raw API responses

Turn a single-line fetch or curl response into an indented structure where the field you need is easy to find.

Pinpoint broken JSON

A trailing comma, single quote or unquoted key fails the parse immediately instead of silently corrupting your data.

Keep payloads private

Sensitive responses with auth tokens are processed in-browser and never sent to a server.

Example: raw input to formatted output

The same payload pasted as one line on the left, formatted with 4-space indentation on the right.

Minified → formatted
{"order":{"id":"A-1009","items":[{"sku":"TS-01","qty":2},{"sku":"MUG","qty":1}],"paid":true,"total":42.5}}
{
    "order": {
        "id": "A-1009",
        "items": [
            {
                "sku": "TS-01",
                "qty": 2
            },
            {
                "sku": "MUG",
                "qty": 1
            }
        ],
        "paid": true,
        "total": 42.5
    }
}

Formatter vs. beautifier — what's the difference?

For JSON, "formatting" and "beautifying" describe the same outcome: readable, indented output. This page leans on the validate-then-format workflow — it's the tool to reach for when you're debugging an API and need to confirm the response is valid JSON before you trust it. If you simply want to tidy a known-good document for reading or committing, our JSON Beautifier does the same job with the same engine. Both run entirely client-side; pick whichever name matches how you think about the task.

When you're ready to ship the JSON over the wire, reverse the operation with a JSON minifier to strip the whitespace back out.

Syntax errors this formatter catches for you

  • Trailing commas after the last element of an object or array — allowed in JavaScript, rejected by JSON.
  • Single quotes around keys or strings instead of the double quotes JSON requires.
  • Unquoted keys such as {name: "x"} rather than {"name": "x"}.
  • Comments — JSON has no comment syntax, so both // and /* */ fail the parse.
  • Unbalanced brackets, missing colons, or a stray NaN / undefined that isn't valid JSON.

Frequently asked questions

Yes. The input is parsed before it's formatted, so if you get clean output your JSON is valid. If it can't be parsed, you'll see an error instead of formatted text — formatting and validation happen in the same step.

Functionally they produce the same readable, indented JSON using the same parse-and-reserialise engine. The Formatter is framed around validating and debugging API output, while the Beautifier is framed around tidying documents. Use whichever name fits your task.

No. Parsing and formatting run entirely in your browser with JavaScript. You can even disconnect from the internet and the tool keeps working, so sensitive payloads stay on your machine.

The most common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or comments — none of which are legal JSON. Fix the flagged issue and the formatted output reappears automatically.

Output uses 4-space indentation, the most common convention for readability. If your project needs 2 spaces or tabs, you can reindent in your editor after copying the result.

Yes. Formatting happens in-memory in your browser, so files up to several megabytes are handled comfortably. Extremely large files depend on your device's available memory.

Need another tool?

Browse the full toolbox or dig into the blog for the engineering behind it.

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