JSON Formatter, Validator and Minifier Online
JSON (JavaScript Object Notation) is the standard data-interchange format for APIs, configuration files, and web applications. This tool parses your input against the strict JSON grammar defined in RFC 8259, pretty-prints valid documents with consistent indentation, and pinpoints syntax errors — a missing comma, an unquoted key, a trailing comma — with their exact location so you can fix them quickly. You can also minify a document, stripping all unnecessary whitespace to reduce payload size.
Everything runs locally in your browser: the JSON you paste is never uploaded to a server, which makes the tool safe for API responses, configuration snippets, and other data you would rather not share. Format a raw single-line API response to inspect its structure, validate a config file before deploying it, or compact a formatted document before embedding it in code.
How it works
The tool parses input with the native JSON.parse engine, which enforces the strict RFC 8259 grammar: double-quoted keys and strings, no trailing commas, no comments. Valid input is re-serialized with JSON.stringify using your chosen indentation for formatting, or with zero whitespace for minification. Parse failures surface the engine's error message and position.
Use cases
- Pretty-printing a raw single-line API response so its structure is readable
- Validating a JSON configuration file before committing or deploying it
- Locating the exact position of a syntax error in a large JSON document
- Minifying JSON to reduce payload size before embedding it in code or sending it over the network
- Cleaning up hand-edited JSON that may have picked up trailing commas or single quotes
- Inspecting webhook payloads and log entries during debugging sessions
Frequently asked questions
How do I format JSON online?
Paste your JSON into the input area and the tool parses it immediately. If the document is valid, it is pretty-printed with consistent indentation so nested objects and arrays are easy to read. If it is invalid, you get the parser's error message with the position of the problem. Nothing is uploaded — parsing happens entirely in your browser.
Why is my JSON invalid?
The most common causes are trailing commas after the last item in an object or array, single quotes instead of double quotes, unquoted property names, and comments — none of which the JSON standard allows. JSON is stricter than a JavaScript object literal, so code that works in JS can still fail validation. The error position reported by the validator points you at the first character the parser could not accept.
What is the difference between formatting and minifying JSON?
Formatting (also called beautifying or pretty-printing) adds line breaks and indentation so humans can read the structure. Minifying does the opposite: it removes every space, tab, and line break that is not inside a string, producing the smallest equivalent document. Both representations contain exactly the same data — machines parse them identically.
Is it safe to paste sensitive JSON into this tool?
Yes. The formatter runs entirely in your browser using the built-in JSON engine, and your input is never sent to a server. That said, standard caution applies to any shared or public computer: clear the page when you are done if the data is confidential.
Does JSON allow comments or trailing commas?
No. The JSON specification (RFC 8259) does not permit comments, trailing commas, single-quoted strings, or unquoted keys. Supersets such as JSON5 and JSONC relax these rules and are used by some tools (VS Code settings, for example), but a strict validator will reject them. If you need to annotate JSON, keep comments in a separate field or use a JSON5-aware pipeline.