Developer Tools
JSON Validator
Validate JSON syntax in your browser. Paste a payload and instantly see whether it parses, plus a friendly error message with line and column if it does not. Great for catching trailing commas, unquoted keys or single quotes before deploying.
Your input is processed locally in your browser. It is not uploaded to Dueneo.
Loading JSON Validator…
How to use
- 1
Paste your JSON
Drop raw JSON from an API response, config file or test fixture into the editor.
- 2
Click Validate JSON
The parser runs instantly in your browser. A green banner means your JSON is syntactically valid.
- 3
Read the error if invalid
When validation fails you get a message, the line/column where the parser stopped, and a short excerpt of that line.
- 4
Fix and re-validate
Editing the input clears the result, so re-click Validate after every fix to confirm.
Common use cases
- Catch a trailing comma before deploying a config file.
- Verify a JSON payload returned by a backend endpoint during debugging.
- Validate hand-edited JSON-LD structured data before publishing.
- Quick sanity check before passing JSON into a build pipeline.
Limitations
- Only syntactic validity is checked — schema and semantic rules are not enforced.
- Inputs larger than 1 MB are rejected to keep the page responsive.
- JSON5 features (single quotes, comments, trailing commas) are reported as invalid because they are not standard JSON.