Fix JSON Errors: A Complete Guide from Beginner to Expert

JSON is strict: one missing comma or extra comma can break parsing. This guide helps you find and fix errors from beginner mistakes to expert edge cases.

Beginner: Common JSON Syntax Errors

1. Trailing commas – JSON does not allow a comma after the last element.

1// BAD
2{ "a": 1, "b": 2, }
3 
4// GOOD
5{ "a": 1, "b": 2 }

2. Single quotes – JSON requires double quotes for keys and strings.

1// BAD
2{ 'name': 'John' }
3 
4// GOOD
5{ "name": "John" }

3. Unescaped characters – Inside strings, quote and backslash must be escaped.

1// BAD
2{ "message": "He said "hi"" }
3 
4// GOOD
5{ "message": "He said \"hi\"" }

Intermediate: Using the Parser and Validators

Use JSON.parse() in a try/catch to get the position of the error:

1function safeParse(str) {
2  try {
3    return JSON.parse(str);
4  } catch (e) {
5    // e.message often includes position, e.g. "Unexpected token } in JSON at position 42"
6    console.error(e.message);
7    return null;
8  }
9}

Tool: Use our [JSON Formatter & Validator](/tools/json-formatter/) to paste your JSON and see exactly where it fails.

Advanced: Encoding, BOM, and Large Files

Expert: Schema Validation and Production Tips

Format and validate in one place: [JSON Formatter](/tools/json-formatter/).