Unexpected Token JSON Error – How to Fix It Instantly
The Unexpected token JSON error occurs when a JSON parser encounters invalid syntax that breaks the expected JSON structure. This is one of the most common JSON errors faced by developers while working with APIs, configuration files, and frontend applications. Even a single extra comma, missing quote, or invalid character can trigger this error.
Detect and fix unexpected token JSON errors instantly using our free browser-based tool.
What Is the “Unexpected Token JSON” Error?
The unexpected token JSON error means the parser found a character or token that violates valid JSON rules. JSON is extremely strict and does not allow flexibility like JavaScript objects.
- Keys must be wrapped in double quotes
- Trailing commas are not allowed
- Brackets and braces must be properly closed
If any of these rules are broken, parsing stops immediately.
Common Causes of Unexpected Token JSON Error
1. Trailing Commas
{
"name": "John",
"age": 30,
}Trailing commas are invalid in JSON.
2. Missing or Invalid Quotes
{
name: "John"
}JSON keys must always use double quotes.
3. Invalid Characters or Comments
{
"status": true // comment
}JSON does not support comments.
4. Incomplete JSON Structure
{
"items": [
{ "id": 1 }
Missing closing brackets cause parsing failures.
Why This Error Is Dangerous
- API responses fail silently
- Applications crash unexpectedly
- Data pipelines break
- CI/CD workflows stop
How to Fix Unexpected Token JSON Error
Step 1: Paste Your JSON
Copy the JSON that caused the error and paste it into the editor.
Step 2: Detect the Error
The tool highlights the exact unexpected token location.
Step 3: Fix & Validate
Automatically repair syntax issues and validate JSON.
When Does This Error Usually Occur?
- Parsing API responses
- Using JSON.parse() in JavaScript
- Validating configuration files
- Copying JSON from logs or terminals
- Frontend frameworks like Angular or React
Best Practices to Avoid This Error
- • Always validate JSON before use
- • Avoid manual edits in production configs
- • Use strict JSON validators
- • Keep JSON minimal and consistent
- • Never add comments or trailing commas
Frequently Asked Questions
What does “Unexpected token JSON” mean?
It means the JSON parser encountered an invalid character or structure.
Is trailing comma allowed in JSON?
No. JSON strictly disallows trailing commas.
Can this error break APIs?
Yes. Invalid JSON responses can cause API consumers to fail.
How can I fix this error quickly?
Use an online JSON fixer to automatically detect and repair syntax issues.