Common JSON Errors & How to Fix Them
Learn about the most frequent JSON mistakes developers make and how to fix them. Use our JSON validator below to check your own code.
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JSON Error Guides
Click any error for a detailed explanation, code examples, and step-by-step fix instructions.
Unexpected Token in JSON
Learn why JSON throws an unexpected token error and how to fix it. Common causes include trailing commas, single quotes, and unquoted keys.
Trailing Comma in JSON
How to fix the trailing comma error in JSON. Unlike JavaScript, JSON does not allow a comma after the last element.
Single Quotes in JSON
JSON requires double quotes for all strings and keys. Learn how to fix the single quotes error.
Unquoted Property Keys in JSON
JSON requires all property names to be wrapped in double quotes. Learn how to fix unquoted key errors.
Missing Comma Between Properties
Learn how to fix the missing comma error in JSON. Every property pair must be separated by a comma.
Duplicate Keys in JSON
Learn why duplicate keys in JSON are problematic and how to fix them. The last value silently overwrites earlier ones.
Unclosed Bracket or Brace in JSON
How to fix unclosed brackets and braces in JSON. Every opening { or [ must have a matching closing } or ].
Invalid Value Type in JSON
JSON only supports strings, numbers, booleans, null, objects, and arrays. Learn how to fix invalid value types.
Invalid Escape Characters in JSON
Learn which escape sequences are valid in JSON strings and how to fix invalid ones.
Invalid Nesting in JSON
Learn how to fix improperly nested objects and arrays in JSON documents.
Invalid Number Format in JSON
Learn the rules for valid numbers in JSON and how to fix formatting errors.
Comments in JSON
JSON does not support comments. Learn why and how to work around this limitation.