Fix invalid JSON.
Understand the error.

Remove trailing commas

A comma separates two properties or array items. It cannot appear immediately before the closing brace or bracket. Remove only the final comma; keep the commas between earlier items.

{"name":"Ada","active":true,}

{"name":"Ada","active":true}

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Use double quotes for keys and strings

JavaScript object literals can use single quotes or unquoted keys, but JSON cannot. Quote each key and string with double quotes. Do not blindly replace every apostrophe: an apostrophe inside a name such as O’Neil is part of the value.

{'name': 'Ada'}

{"name":"Ada"}

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Separate properties with a comma

The parser may point to the second key because that is where it discovers the missing separator. Inspect the text immediately before the reported location as well as the highlighted character.

{"name":"Ada" "active":true}

{"name":"Ada","active":true}

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Escape backslashes in Windows paths

A backslash starts an escape sequence in JSON. Write two backslashes to represent one literal backslash. For a line break inside a string, use the escape sequence \n instead of placing a raw line break between the quotes.

{"path":"C:\Users\Ada"}

{"path":"C:\\Users\\Ada"}

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Use JSON values instead of JavaScript values

Boolean literals are lowercase true and false. JSON has no undefined, NaN or Infinity values. Use null only when it correctly represents your data, or remove the property if your application expects it to be absent. Null and a missing property are different.

{"active":True,"result":undefined}

{"active":true,"result":null}

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Resolve duplicate keys deliberately

Repeated names can produce different behavior across parsers. JSON Workpad rejects them during validation to avoid silently losing a value. In this example, keeping 4 is a deliberate choice, not an automatic repair. Its comparison tool instead uses the last occurrence and displays a warning.

{"expiry_buffer":3,"expiry_buffer":4}

{"expiry_buffer":4}

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When valid JSON still fails in your application

Valid syntax does not guarantee that an API accepts the document. An API might require an integer instead of a string, a particular date format or a mandatory field. Check its schema and error response after syntax validation succeeds.

Keep identifiers precise. JSON Workpad preserves numeric text such as 9007199254740993 during formatting. Other software may round long numbers when it parses them; follow your API contract when choosing between a number and a string.

Compare the result before sending it

Use JSON comparison to inspect property and value changes. Object key order is ignored, while array order matters. To review punctuation, spacing or the original text exactly as entered, use text comparison.

For data imports, convert CSV to JSON while keeping cell values as strings. For spreadsheet exports, convert flat JSON records to CSV.

Privacy and limits

Validation runs in your browser without sending your JSON to a server. The input limit is 1 MB and the nesting limit is 120 levels. The validator checks syntax and duplicate keys; it does not automatically repair or rewrite your input.

Validate your JSON → · Read the JSON format specification (RFC 8259)