Even experienced developers encounter the dreaded "Unexpected token" error. JSON is strict, and unlike JavaScript, it does not forgive small syntax mistakes.
The "Big Three" Syntax Errors
If your JSON isn't parsing, it is likely due to one of these three common culprits:
1. The Trailing Comma
In JavaScript objects, a comma after the last item is allowed. In JSON, it is forbidden.
Wrong: { "id": 1, "name": "Tool", }
Right: { "id": 1, "name": "Tool" }
2. Single Quotes
JSON standard strictly requires double quotes for both keys and string values. Single quotes will cause an immediate parsing error.
Wrong: { 'name': 'UtilityKit' }
Right: { "name": "UtilityKit" }
3. Unquoted Keys
In standard JS, you can write { id: 1 }. In JSON, the key must be a string.
Wrong: { id: 1 }
Right: { "id": 1 }
How to Find the Error Instantly
Scanning thousands of lines of code for a single quote is inefficient. Using a validator allows you to copy-paste your code and immediately see a red flag on the exact line number where the syntax breaks.
Validate Your Code
Paste your JSON here to find syntax errors instantly.
Conclusion
Understanding these strict rules is the first step, but having a tool to catch them is the second. Don't waste time debugging syntax manually—use a validator to keep your workflow smooth.