Causes and Solutions for JSON "Unexpected token" Errors
Trailing commas, single quotes, and comments—syntax that works in JS will fail in JSON. Put your code through a formatter to instantly identify these issues.
The True Identity of the Error
This error occurs when the string passed to JSON.parse() violates JSON syntax rules.
JSON is completely different from a JavaScript object literal and adheres to much stricter rules.
Common Causes
| NG Pattern (Works in JS, FAILS in JSON) | Correct JSON |
|---|---|
| Trailing comma { "name": "Taro", } | Remove the final comma { "name": "Taro" } |
| Missing quotes on key { age: 25 } | Enclose in double quotes { "age": 25 } |
| Single quotes { 'role': 'admin' } | Use double quotes { "role": "admin" } |
| Comments { "data": [] // memo } | Comments are disabled { "data": [] } |
Debugging Steps
-
Check the error log — look around
at position Nfor the culprit. -
Paste into a formatter — let a tool automatically highlight syntax errors.
-
Fix and Parse — correct the pointed-out issues, and rerun
JSON.parse().
If your output shows [object Object] when using console.log(), it’s already an active object, not a string. There’s no need to pass it into JSON.parse().
Check Syntax with a Tool
By pasting it into a JSON formatter, syntax errors will be highlighted. Because it runs securely within your browser, checking API response payloads is safe.
🧪 Syntax Check with JSON Formatter
Instantly detect errors just by pasting. Data is never sent to any server.