JSON Formatter & Validator
Format, validate, and minify JSON instantly in your browser. Zero network requests — your data never leaves your device.
Formatter
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What Is a JSON Formatter?
JSON Formatter parses your input against the canonical specification (RFC 8259 / ECMA-404) and reformats it for readability or compactness. Strict JSON forbids three things you might be tempted to type: comments (no // or /* */), trailing commas after the last array or object element, and unquoted object keys. Tools like VS Code use JSON-with-comments (JSONC) for tsconfig.json, and JSON5 extends strict JSON with both — but neither is accepted by RFC-8259 parsers like JSON.parse, Go's encoding/json, or Python's json module. If your file starts with the bytes EF BB BF (UTF-8 BOM, often added by Notepad on Windows), most parsers will reject it; the formatter strips the BOM transparently. The tool also recognises JSON Lines (.jsonl / NDJSON) — one independent JSON value per line, common in log streams and ML datasets — and offers to format each line individually. Errors point to the exact byte offset, line, and column where parsing fails.
How to Use the JSON Formatter
Paste raw JSON into the input panel. Click Pretty print for indented output (2 spaces is the npm/yarn convention, 4 spaces is Python's json.tool default), or Minify to remove all insignificant whitespace for production payloads. Validate only checks syntax without rewriting the buffer. If parsing fails, the error shows the line and column, plus a context window showing the surrounding characters — usually the broken token is a missing quote, a stray comma, or a misescaped backslash. For .jsonl input, each line is parsed independently and shown as a numbered list. The byte counter at the bottom shows input size live (useful when an API caps request bodies). Copy and Download buttons preserve the chosen indentation. The tool accepts any valid JSON value at the top level — object, array, string, number, boolean, or null.
Why Valid JSON Matters in Development
JSON's strict syntax is a feature: it constrains what a producer can emit so consumers don't need a forgiving parser. A trailing comma in a JavaScript object literal is fine; in JSON it crashes the entire payload. This rigidity is why JSON displaced XML for API interchange — there is essentially one way to write { "a": 1, "b": 2 }. The cost shows up at the boundaries: an .env file converted to JSON loses comments, a config file copy-pasted from Stack Overflow inherits a smart-quote (U+201C) that JSON parsers reject, and a webhook signature compares two JSON strings that look identical but differ in whitespace. Reformatting through a known-good parser normalises the bytes so subsequent comparisons are reliable. Validating JSON before committing also catches errors at desk time instead of in CI, where a five-minute pipeline failure costs more than a five-second local check.
Frequently Asked Questions
Does this upload my JSON?
No. Formatting and validation happen entirely in your browser. Nothing is sent to TeaFun servers.
Can it minify JSON too?
Yes. Use Minify to remove whitespace for compact payloads, or Pretty print to make JSON easier to read.
What happens on invalid JSON?
The tool shows the parser error plus the best available line and column so you can fix the broken part quickly.
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