JSON Formatter & CSV Converter – Format JSON Online Free

How to Format, Validate or Convert

Pick a mode, paste your data into the Input box, click Process and use Copy Output to copy the result. Each mode does one job:

• Format JSON pretty-prints valid JSON with a two-space indent and shows the number of keys and the output size.
• Minify JSON removes whitespace and reports how many bytes were saved.
• Validate JSON checks syntax only. It confirms the text parses as JSON, but it does not check the data against a JSON Schema.
• JSON → CSV and CSV → JSON convert between the two formats, following the rules below.

Switching mode clears the previous result. Results longer than 200,000 characters are shown as a preview, and Copy Output always copies the full result.

JSON to CSV and CSV to JSON: What to Expect

When you convert JSON to CSV:

• An array of objects becomes one row per object. The columns are every key that appears in any object, so missing values become empty cells.
• A single object becomes one row, and an array of plain values becomes a single value column.
• Nested objects and arrays are not flattened. They are kept as JSON text inside the cell.
• Values that contain commas, quotes or line breaks are wrapped in quotes, with inner quotes doubled.
• If a cell starts with =, +, - or @, the tool warns you, because spreadsheet apps such as Excel may run it as a formula when you open the file. The CSV itself is not changed.

For example, this JSON:

[
  { "id": 1, "name": "Ada", "tags": ["admin", "ops"] },
  { "id": 2, "name": "Lin, Wei", "active": true }
]

becomes this CSV:

id,name,tags,active
1,Ada,"[""admin"",""ops""]",
2,"Lin, Wei",,true

When you convert CSV to JSON:

• The first row is used as the headers, and you need at least one data row below it.
• Quoted fields can contain commas, doubled quotes and line breaks.
• Empty cells become null.
• Numbers are converted only when the value stays exactly the same, so 10001 becomes a number but 007 and 1.50 stay as text.
• true and false stay as text rather than becoming booleans.

Common JSON Errors

If your input is not valid JSON, the tool shows the error message from your browser instead of an output. The usual causes are:

• A trailing comma after the last item in an object or array.
• Single quotes instead of double quotes around strings or keys.
• Keys without quotes, as in JavaScript object literals.
• Comments, or values such as NaN that are not part of JSON.

Read our guide to formatting JSON online for more background. To compare two versions of a JSON file, use the Diff Checker, and to create sample JSON or CSV data for testing, try the Dummy Data Generator.