Format and validate JSON instantly, pinpoint syntax errors, and preview repairs before applying them—all in your browser.
JSON Formatter
Format and validate JSON instantly, pinpoint syntax errors, and preview repairs before applying them—all in your browser.
About JSON Formatter
Parse before formatting
The formatter validates with strict JSON parsing before applying consistent indentation. If it finds a missing comma, quote, or bracket, it shows the line and column and may offer a repair preview. Your original input stays unchanged until you apply that repair.
Review payloads with stable indentation
Choose spaces or tabs to match the codebase you are reviewing. This is useful when comparing API responses, checking nested configuration, or pasting a readable payload into a pull request or issue.
FAQ
Common questions and answers about this topic.
What does this JSON formatter do?
It auto-formats and validates your JSON data with proper indentation, making it easy to read, debug, and share.
Can I customize the indentation?
Yes, choose 2 or 4 spaces, or tabs. JSON convention typically uses 2 spaces.
Does it validate the JSON?
Yes. Strict JSON parsing identifies the error line and column and shows nearby source, so you can inspect the problem before changing the input.
Can it repair invalid JSON automatically?
It can propose a repair for supported syntax errors and show the exact changes first. Nothing is applied automatically—you choose whether to apply or copy the repaired JSON.
How large can the JSON input be?
The input limit is 5 MB in UTF-8. Formatting and validation run in a browser worker; larger input stops with a size message instead of starting the operation.
Is my data sent to any server?
No, JSON formatting is handled entirely in your browser. Your data is parsed and re-formatted locally with JavaScript — nothing leaves your device.