Free Online JSON Fixer, Validator and Formatter for Developers
JSON is the default data format of modern software — REST APIs, cloud configuration files, CI/CD pipelines, serverless function payloads, analytics events and, increasingly, the structured output of large language models. It is also unforgiving: one missing comma, one smart quote pasted from a document, or one unclosed bracket and your parser stops dead with a cryptic message such as Unexpected token } in JSON at position 214. This tool reads that broken text, repairs the most common structural faults automatically and hands back clean, indented, standards-compliant JSON you can drop straight into your codebase.
What the auto-fix engine repairs
- Missing commas between object entries and array items across line breaks.
- Trailing commas that are legal in JavaScript but rejected by strict JSON parsers.
- Single-quoted strings and unquoted object keys, converted to double-quoted JSON keys.
- Unclosed brackets and braces, balanced in the correct nesting order.
- Language literals such as Python
None,True,Falseand JavaScriptundefined/NaN. - Markdown code fences and inline comments that AI chat models wrap around their responses.
Why AI output breaks JSON parsers
Language models generate text token by token, so a long response can be truncated by a context limit mid-object, or drift into JavaScript-flavoured syntax because that is what dominates their training data. Teams shipping LLM features spend a surprising amount of engineering time on this exact problem. Pasting the raw completion here gives you a parseable object in one click, which is often faster than adding another retry loop or a schema-repair prompt to your production pipeline while you are still debugging.
Privacy: nothing is uploaded
The entire repair, validation and formatting pipeline is plain JavaScript executing in your own browser tab. Your payload is never transmitted to a server, never logged, and disappears when you close the page. That makes it safe for API keys embedded in configuration samples, customer records inside a bug report, Stripe or PayPal webhook bodies, cloud infrastructure templates, and internal analytics exports that must never leave your machine — a guarantee that server-side JSON validators cannot make.
Minify for production, format for review
Use Auto-Fix & Format for two-space indentation when you are reading a payload, reviewing a pull request or writing documentation. Use Minify to strip every unnecessary byte before embedding JSON in an environment variable, a query string, a database column or an HTTP response, where smaller payloads mean lower bandwidth bills and faster response times. The Copy button places the result on your clipboard in one click.