JSON Formatter & Validator
Pretty-print, validate, and minify JSON with configurable indentation, detailed error positions, and document statistics. Runs entirely in your browser.
Input JSON
How it works
- Paste JSON, choose an indentation, and click Format — the document is parsed and re-serialized with clean indentation.
- Minify strips all whitespace to produce the smallest valid representation.
- If the document is invalid, the error shows the exact message plus line and column, so you can jump straight to the problem.
- Statistics update automatically after each run.
About JSON Formatter & Validator
Pretty-printing turns a wall of JSON into an indented, readable tree, which makes nested structures and subtle mistakes — a missing comma, a trailing comma, a stray quote — far easier to spot. Formatting never changes the meaning of the document: it only re-serializes the parsed value, so the output is guaranteed to be valid JSON.
Use this tool before sharing JSON in code review, pasting payloads into documentation, or debugging API responses. Minify when you need the smallest payload for a URL query, a storage cell, or a log line. Since parsing happens on your device, even sensitive configuration or private API responses can be formatted without ever leaving your browser.
What the formatter actually does
The formatter parses your JSON with a real parser rather than a regular expression, so it only reformats input that is genuinely valid. Indentation is configurable — two spaces, four spaces, or tabs — and the output is re-serialised from the parsed structure, which means key order is preserved exactly as it appeared in the input.
When validation fails, the error is reported with the line and column where parsing stopped, plus the token that caused it. That detail matters more than it sounds: "Unexpected token }" on a 4,000-line response tells you nothing, while line 2,041 column 18 narrows the search to a few characters.
When to reach for it
Use it before committing a config file, when a hand-edited JSON file has lost its shape after a merge conflict. Use it when you receive minified JSON from an API and need to read it. Use it as a first pass before a schema validator — formatting first makes the error position readable.
It is not a schema validator. If you need to know whether a document matches a contract rather than merely whether it parses, follow this with the JSON Schema Validator on the same site.
What it does not do
The tool never sends your JSON anywhere, so a very large document will be processed at whatever speed your own machine manages — there is no server-side queue to wait for. Duplicate keys are collapsed to the last occurrence, matching JavaScript object semantics, which is worth knowing if your source has duplicates you care about.
Next steps
- JSON Minify— compress the formatted output
- JSON to Zod Schema— turn this into a TypeScript validator
- JSON Schema Validator— verify against a schema
Frequently Asked Questions
How do I format JSON online for free?
Can I pretty print minified JSON?
Is my data sent to a server?
Do I need an account or API key?
Can I use these tools offline?
All processing happens in your browser. No uploads, no tracking, no servers. Your API keys, configs, and private payloads stay private — 100% client-side.