Common JSON Validation Errors and How to Fix Them
A practical guide to common JSON parsing and validation errors with quick fixes for each case.
Last updated: May 4, 2026
1) Unexpected token at position X
This usually means invalid JSON syntax. Common causes are trailing commas, missing quotes around keys, or single quotes instead of double quotes.
2) Unexpected end of JSON input
The document was cut off or has an unclosed object/array. Check for missing closing braces (}) and brackets (]) at the end of payloads.
3) Invalid control character
Raw line breaks or tabs inside JSON strings can break parsing. Escape them as \n and \t, or keep them outside string values.
4) Number format errors
JSON numbers cannot contain commas and must not have trailing decimal dots. Use 1000 instead of1,000, and 1.5 instead of 1..
Quick validation workflow
- Format the payload first to reveal structure clearly.
- Fix the first reported error before chasing later ones.
- Re-validate after every change to avoid introducing new syntax issues.