What are the most common JSON errors?

The most common JSON errors are: trailing commas after the last item in an object or array, using single quotes instead of double quotes, missing commas between key-value pairs, unquoted property keys, and mismatched or missing curly braces and square brackets.

Why does JSON not allow trailing commas?

The JSON specification (RFC 8259) strictly forbids trailing commas. This is different from JavaScript which allows them. When you copy JS object literals into JSON, trailing commas are one of the most common causes of JSON parse errors.

Can I use single quotes in JSON?

No. JSON requires all strings — both keys and values — to be wrapped in double quotes. Single quotes cause a JSON parse error. Replace all single quotes with double quotes to fix this error.

What does 'Unexpected token at position X' mean?

This error means the JSON parser encountered a character it did not expect at that character position in your string. Count from the beginning of your JSON to position X to find the problematic character. Common causes are a stray comma, an unescaped quote, or a missing colon.

Can I have comments in JSON?

No. Standard JSON does not support comments (// or /* */). If your JSON contains comments, you will get a parse error. Remove all comments before validating or use JSONC format, which is specific to VS Code configuration files.

Fix JSON Error Online

Paste your broken JSON and get clear, precise error messages that tell you exactly where and what went wrong — then fix it in seconds.

Input JSON

Output / Error Details

Options

Indent: Sort keys A–Z

How to Fix JSON Errors Online

When your application throws a JSON parse error, the fastest way to diagnose it is to paste the raw JSON into a dedicated debugger that gives you an exact error location. The tool above uses JavaScript's native JSON.parse() to produce precise error messages — the same engine your browser and Node.js use — so the output perfectly mirrors what your code sees.

Click Validate to see the error message instantly. Click Format to attempt formatting — if the JSON is broken, the error is displayed in the status bar with the character position of the fault.

Step-by-Step: Debug a JSON Error

Paste the broken JSON into the Input JSON field above
Click Validate to get the exact error message and position
Note the character position in the error (e.g. "position 45") — count from the start of your JSON or use Ctrl+F in a text editor
Fix the issue — see the common errors guide below
Click Format to confirm the fix — a green status message means your JSON is now valid

Most Common JSON Errors and How to Fix Them

❌ Trailing comma

Invalid: {"name":"Alice","age":30,}

Fixed: {"name":"Alice","age":30} — remove the comma after the last item

❌ Single quotes instead of double quotes

Invalid: {'name':'Alice'}

Fixed: {"name":"Alice"} — JSON requires double quotes everywhere

❌ Unquoted keys

Invalid: {name:"Alice"}

Fixed: {"name":"Alice"} — all keys must be quoted strings

❌ Comments in JSON

Invalid: {"name":"Alice" // user name}

Fixed: Remove all // ... and /* ... */ comments — JSON does not support them

Tips for Avoiding JSON Errors

Always use a JSON validator before deploying config files or API payloads
When building JSON from code, use JSON.stringify() instead of string concatenation — it handles escaping automatically
Never copy JavaScript object literals directly into JSON without converting single quotes and removing trailing commas
Use a linter or editor plugin (like VS Code's built-in JSON language server) to catch errors as you type

Related JSON Tools

🛠️ JSON Formatter ✨ JSON Pretty Print ✅ JSON Validator ⚠️ Format with Errors 🔐 Base64 Encoder 🔗 URL Encoder

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