Developer Tools
JSON Validator
Check whether your JSON is valid and locate errors.
Runs locally in your browser — your input is not uploaded.
How to use
- Paste the JSON you want to check.
- Click Validate.
- If the document is invalid, read the error message and optional line/column hints.
- Fix the issue and validate again until it passes.
About this tool
A JSON validator checks that text conforms to the JSON grammar. It does not check whether the data matches a particular schema — only that it is syntactically valid.
When the JavaScript parser reports a character position, ToolForge maps that position back to a line and column so you can jump to the problem quickly.
Validation happens locally. Your payload is never transmitted to ToolForge.
Examples
Catch a trailing comma
This document is invalid because of the comma after 2.
{"a":1,"b":2,}FAQ
Does this validate against a JSON Schema?
No. This tool checks syntax only. Schema validation is a separate concern and may be added in a future premium tool.
Why might line numbers be approximate?
Browsers expose different error message formats. When a character position is available we convert it to line/column; otherwise we show the raw parser message.
Related tools
- JSON EditorEdit, format, repair, query, compare, and explore JSON in text, tree, and table modes.
- JSON FormatterFormat, minify, and validate JSON in your browser.
- JSON to CSVConvert a JSON array into CSV for spreadsheets.
- JWT Decoder / GeneratorDecode or generate JWTs locally — secrets never leave your browser.
Want more power later?
Premium tools, higher limits, and API access are on the roadmap. V1 stays free and private in your browser.