7 Common JSON Errors and How to Fix Them (with Examples)

Almost every "Invalid JSON" message comes from one of seven mistakes. Learn them once and you will fix most payloads in under a minute.

1. Missing comma

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

Fix: {"a": 1, "b": 2}. Two values in an object or array must be separated by a comma.

2. Trailing comma

{"a": 1,}

Fix: remove the last comma. Strict JSON forbids it (JSON5 allows it — see JSON vs JSON5).

3. Missing or single quotes

{name: 'Ada'}

Fix: {"name": "Ada"}. Keys and strings need double quotes.

4. Unmatched braces or brackets

{"items": [1, 2}

Fix: close in reverse order — {"items": [1, 2]}. Formatting with the JSON formatter makes these obvious.

5. Invalid values

{"active": undefined}

Only strings, numbers, booleans, null, objects and arrays are allowed. Use null, not undefined or functions.

6. Malformed strings

{"bio": "line one
line two"}

Fix: escape the newline — {"bio": "line one\nline two"}. The JSON escape tool does this for you.

7. Extra text after the document

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

One JSON document per parse. Wrap multiples in an array or use JSON Lines tooling.

Fastest fix workflow

1. Paste into the JSON validator and press Go to error.
2. Fix the character at that line and column.
3. Press Format in the JSON formatter to confirm.