Why is a trailing comma an error in JSON?

The JSON specification (RFC 8259) does not permit trailing commas. Many programming languages allow them for convenience, but JSON was designed to be a minimal, strict format. A comma implies another element follows — if there is none, it is a syntax error.

Where are trailing commas most commonly found in JSON?

The most common places: after the last property in an object { "a": 1, "b": 2, } and after the last item in an array ["a", "b", "c",]. Trailing commas in deeply nested structures are harder to spot without a tool.

My code editor auto-adds trailing commas — how do I fix this?

Configure your editor or formatter to disable trailing commas for JSON. In VS Code, add "json.format.enable": true and ensure your Prettier config has "trailingComma": "none" for JSON files. In the meantime, use FixTools to quickly find and fix any that slipped through.

Does JavaScript allow trailing commas in JSON.parse?

No. JSON.parse() is strict and will throw SyntaxError for trailing commas. However, JavaScript object literals in source code do allow trailing commas — that is why it is easy to confuse the two.

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Fix Trailing Comma in JSON

You've seen this error: SyntaxError: Unexpected token, or Trailing comma is not allowed. You know there is a stray comma somewhere in your JSON — probably after the last item in an array or the last property in an object — but scrolling through hundreds of lines to find it is tedious. Paste your JSON into FixTools and it will highlight the exact line with the trailing comma so you can remove it and move on.

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Pinpoints trailing comma location instantly

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Works with nested objects and arrays

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Validates after fixing to confirm the fix

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How to use this tool

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Paste the JSON with the trailing comma error and click Validate to find its exact location.

How It Works

Step-by-step guide to fix trailing comma in json:

1
Paste the JSON with the trailing comma
Copy your JSON and paste it into the FixTools editor.
2
Click Validate
FixTools identifies the trailing comma and tells you its exact line and column.
3
Remove the trailing comma
Delete the comma after the last element in the reported array or object.
4
Validate again
Click Validate to confirm the error is gone.