How to Fix Invalid JSON from API Response

1. Trailing Commas in Objects and Arrays

JavaScript allows trailing commas. JSON does not. This is the #1 cause of broken JSON from API responses.

{
  "name": "Alice",
  "age": 30,   // ← trailing comma
}

Fix: Remove the comma after the last element. If you have multiple objects, only the last one should omit the trailing comma. Paste it into a repair tool and it handles this automatically.

2. Single Quotes Instead of Double Quotes

Some APIs or hand-written configs use single quotes. JSON spec requires double quotes for both keys and string values.

{
  'name': 'Alice',
  'age': 30
}

Fix: Replace all single quotes with double quotes — but be careful not to touch apostrophes inside string values. A proper repair tool handles this correctly by parsing context, not doing a blind string replace.

3. Unquoted Property Keys

JavaScript object literals allow unquoted keys. JSON does not. This is common in hand-written configs or legacy API responses.

{
  name: "Alice",
  age: 30
}

Fix: Wrap every key name in double quotes. The repair tool automatically wraps all unquoted property names.

4. Missing or Mismatched Brackets

Truncated responses, copy-paste errors, or incomplete logs can leave JSON with missing closing brackets.

{
  "users": [
    {"id": 1, "name": "Alice"},
    {"id": 2, "name": "Bob"}
  ]
}

Fix: Count your opening and closing braces / brackets. They must match exactly. The repair engine auto-inserts missing closing delimiters.

5. Comments Inside JSON

JSON does not support comments. Period. But many developers add them, especially when extracting JSON from code or configuration files.

{
  // User profile
  "name": "Alice",    /* inline comment */
  "age": 30
}

Fix: Strip all comments before parsing. The repair tool removes both // and /* */ comments automatically.

6. Broken JSON from ChatGPT / Claude / LLMs

Large language models often wrap JSON in markdown code blocks, use mixed quotes, add trailing commas, or include explanatory text around the JSON.

Here's the JSON you requested:
```json
{
  "name": "Alice",
  'age': 30,
}
```

Fix: Strip markdown wrappers, fix quotes, remove trailing commas. The tool handles all of these in one pass — just paste the raw LLM output.

Best Practices to Avoid Broken JSON

• Validate early. Run every API response through a validator before using it in code.
• Don't hand-edit JSON. Use a proper JSON editor with syntax highlighting and validation.
• Check LLM output. Always repair AI-generated JSON — they almost always have minor syntax errors.
• Use schema validation. For important data structures, validate against a JSON Schema.
• Export to spreadsheet after repair. Once fixed, use our guide to convert nested JSON to CSV to bring the data into Excel.

Related Tools

Frequently Asked Questions

Looking for more guides? See the full JSONXX How To index.