What a JSON validator actually checks
A validator parses the raw text and checks whether the JSON follows the strict JSON grammar. It is not looking for pretty formatting first; it is checking whether the data can be read safely.
This matters for API requests, config files, webhook payloads, and test fixtures because one small syntax issue can break the whole document.
- Missing commas between fields
- Single quotes instead of double quotes
- Trailing commas in arrays or objects
- Broken nesting or unmatched braces
How to read JSON validation errors
Most validation errors point to a line and column. Start there, but also inspect the few characters before it because the real issue is often just above the marker.
If the parser says unexpected token or unexpected end of input, check the surrounding braces, brackets, quotes, and commas first.
A practical fix workflow
Paste the payload, read the first syntax error, fix only that issue, then validate again. Avoid changing multiple parts at once because that makes debugging slower.
Once the JSON becomes valid, beautify it so nested objects and arrays are easier to inspect and review with teammates.