✅ JSON Validator
Validate JSON syntax free online with precise error locations. Catch trailing commas and quote errors instantly, no upload.
✅ JSON Validator
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About the JSON Validator Tool
JSON is unforgiving by design. There are no comments, no trailing commas, no single quotes, and no unquoted keys — restrictions that make parsing fast and unambiguous, but also mean a single stray character invalidates an entire file. Configuration files that silently fail to load are very often a trailing comma somewhere on line 340.
This validator parses your input and reports precisely where and why it fails, so you can fix the actual problem instead of scanning hundreds of lines by eye. Validation runs in your browser, which means configuration containing API keys or credentials is never transmitted.
How to Use JSON Validator
- Paste the JSON you want to check.
- Validation runs immediately.
- If invalid, read the reported position and reason for the failure.
- Correct the issue and revalidate until it passes.
When to Use This Tool
- Debugging a configuration file that an application refuses to load
- Verifying an API payload before sending a request
- Checking hand-edited JSON for syntax mistakes
- Validating data files before committing them to a repository
- Confirming that generated JSON output is well-formed
Things Worth Knowing
- This checks syntax only. Whether the data matches an expected schema is a separate question.
- JSON does not permit comments. Any // or /* */ will cause a failure.
- Trailing commas are the single most common cause of invalid JSON.
Quick Facts
| Tool name | JSON Validator |
| Category | Data Converters |
| Price | Free — no account, no trial, no watermark |
| Where it runs | Entirely in your browser (client-side) |
| Files uploaded | None — your data never leaves your device |
| File size limit | None imposed; limited only by device memory |
| Works offline | Yes, once the page has loaded |
| Platforms | Windows, macOS, Linux, Android, iOS |
Frequently Asked Questions
Why is a trailing comma not allowed?
The JSON specification simply forbids it. JavaScript object literals permit trailing commas, which is why the mistake is so common — but JSON is a stricter subset and parsers reject it.
Can I use comments in JSON?
No. The format has no comment syntax. If you need annotated configuration, use JSON5, YAML, or a dedicated comment field within the data itself.
Does this validate against a schema?
No, this checks structural syntax only. Schema validation — confirming required fields, types, and value constraints — requires a JSON Schema validator.
Are single quotes valid in JSON?
No. All strings and keys must use double quotes. Single quotes are valid JavaScript but invalid JSON.