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
Fix the unexpected token error in JSON fast. See why parsers fail on trailing commas, single quotes, unquoted keys, and comments, with clear examples.
Trailing Comma in JSON
Fix the trailing comma error in JSON quickly. Unlike JavaScript, JSON forbids a comma after the last element, and our examples show you exactly how.
Single Quotes in JSON
JSON requires straight double quotes for every string and key, so single quotes always break parsing. Learn how to fix the single quotes error fast.
Unquoted Property Keys in JSON
JSON requires every property name wrapped in double quotes, so bare keys fail. Learn how to fix unquoted key errors when converting JavaScript objects.
Missing Comma Between Properties
Fix the missing comma error in JSON the right way. Every key-value pair and array element must be separated by a comma, and our examples show where.
Duplicate Keys in JSON
Learn why duplicate keys in JSON cause silent data loss and exactly how to fix them. The last value quietly overwrites earlier ones, hiding real bugs.
Unclosed Bracket or Brace in JSON
Fix unclosed brackets and braces in JSON with confidence. Every opening curly brace or square bracket needs a matching close, and we show you exactly how.
Invalid Value Type in JSON
JSON only supports strings, numbers, booleans, null, objects, and arrays. Learn how to fix invalid value types like undefined, NaN, Infinity, and dates.
Invalid Escape Characters in JSON
Learn which escape characters are valid in JSON strings and how to fix the invalid ones. Windows file paths and regex patterns are the usual culprits.
Invalid Nesting in JSON
Learn how to fix improperly nested objects and arrays in JSON documents. We show why a single structural slip cascades and how to correct it cleanly.
Invalid Number Format in JSON
Learn the rules for valid numbers in JSON and how to fix format errors. No leading zeros, hex, octal, trailing dots, or plus signs are allowed here.
Comments in JSON
JSON does not support comments of any kind. Learn why Crockford removed them and how to document your config files using JSONC, JSON5, or comment keys.