JSON Formatter
Why use a private JSON formatter?
Most online JSON formatters send your data to a remote server for processing. That means your API responses, config files, and internal data structures leave your machine — even if the site claims to delete them immediately.
formatvault formats and validates JSON entirely inside your browser using the native JavaScript engine. Your data never touches a network request. This matters most when working with JWTs, database exports, environment configs, or anything that could contain credentials or PII.
How it works
When you paste or upload JSON, the formatter runs JSON.parse() directly in the browser tab — the same engine your application uses. For relaxed syntax (trailing commas, comments), it switches to the json5 library. Files larger than 5 MB are streamed through a Web Worker so the UI stays responsive.
Output is re-serialized with JSON.stringify() using your chosen indentation (2 spaces, 4 spaces, or tabs). All processing happens locally — closing the tab discards everything immediately.
Common use cases
- Formatting API responses from Postman, curl, or browser DevTools
- Validating JSON config files before deployment (package.json, tsconfig.json, .eslintrc)
- Debugging minified JSON payloads from third-party services
- Sorting keys alphabetically to make diffs easier to read
- Comparing two JSON blobs side-by-side with the built-in diff view
- Querying nested data with JSONPath without writing code
- Formatting large database exports (up to 500 MB) via streaming
- Reviewing JSON that contains credentials or PII without uploading it
Frequently asked questions
- Is my JSON data safe?
- Yes. All processing happens in your browser tab. No data is sent to any server, logged, or stored anywhere. You can verify this by opening DevTools → Network and observing zero outbound requests when you format.
- What is the maximum file size?
- Files up to 500 MB are supported. Files above 5 MB are automatically processed in a Web Worker using a streaming parser, so the UI stays responsive throughout.
- Does the formatter work offline?
- Yes, once the page has loaded. All formatting logic is bundled with the app. No network access is required to format, validate, or minify JSON.
- What is JSON5 and when should I use it?
- JSON5 is a superset of JSON that allows trailing commas, single-quoted strings, and comments. It is commonly used in config files (like Babel or ESLint configs). Enable JSON5 mode when standard JSON.parse() rejects your input.
- How does JSONPath querying work?
- Enter a JSONPath expression (e.g. $.store.book[*].author) in the query field and the formatter extracts matching values in real time. Useful for exploring large nested payloads without writing code.
- Can I format minified JSON?
- Yes. Paste any minified JSON string and the formatter will pretty-print it instantly with your chosen indentation. The minify button does the reverse.