JSON Error Messages Explained

Developers encounter the same JSON parse errors repeatedly. This guide covers the 12 most common error messages with verified engine output, plain-English explanations, and code examples showing the invalid input and how to fix it.

• Unexpected token u in JSON at position 0
• Unexpected end of JSON input
• Unexpected token o in JSON at position 1
• Unexpected token < in JSON at position 0
• Trailing comma in JSON
• Single quotes in JSON are not allowed
• Unexpected string in JSON
• Bad control character in string literal in JSON
• Unterminated string in JSON
• Unexpected non-whitespace character after JSON
• Converting circular structure to JSON
• is not valid JSON