JSON Formatter & Validator
Pretty print, minify, and validate JSON instantly in your browser. No data is sent to any server.
Frequently Asked Questions
ajv (JavaScript), jsonschema (Python), and justinrainbow/json-schema (PHP) perform the validation. It is widely used in API documentation (OpenAPI), CI pipelines, and configuration file validation.
// … and /* … */), trailing commas, single-quoted strings, unquoted keys, and hex literals — making it more comfortable for humans to write by hand. JSONC (JSON with Comments) is a lighter extension used by Visual Studio Code for configuration files; it adds only comments and trailing commas. Neither is valid JSON — standard JSON.parse() will reject them. Use dedicated parsers (json5 npm package, VS Code's built-in JSONC parser) to process them.
JSONStream or oboe.js in Node.js, ijson in Python, or JsonReader in Java — to process records one at a time. On the command line, jq is the standard tool for querying, filtering, and transforming JSON of any size efficiently. For files above ~100 MB, consider converting to a columnar format like Parquet or NDJSON (newline-delimited JSON, one object per line) for streaming compatibility.
Content-Type: application/json with a JSON body in POST/PUT/PATCH requests; servers respond with JSON and the same header. Keys should use camelCase or snake_case consistently (follow the API's convention). Dates are typically encoded as ISO 8601 strings ("2024-01-15T12:00:00Z"). Large numbers beyond JavaScript's safe integer range (2⁵³ − 1) should be sent as strings to avoid precision loss in the client.
About This JSON Formatter
This free JSON formatter prettifies minified JSON with configurable indentation and validates that the input is well-formed. Paste any JSON string — minified or already formatted — and instantly see a readable, indented version or an error message with the exact problem location.
Minified JSON is compact for network transmission but unreadable for debugging. Formatting JSON is one of the most common developer tasks when inspecting API responses, configuration files, and log output.
When to use this tool
- Prettifying API responses for easier reading and debugging
- Validating JSON config files before deployment
- Minifying JSON for a production payload
- Spotting syntax errors like trailing commas or missing quotes
Standards & References
How JSON Formatting Works
Three operations happen in sequence every time you click Format, Minify, or Validate:
Parse
The browser's native JSON.parse() attempts to parse your input. Any syntax error is caught and surfaced with the error message from the engine, pointing you to the offending location.
Transform
For Format: JSON.stringify(obj, null, indent) re-serializes with your chosen indentation. For Minify: JSON.stringify(obj) with no whitespace — the smallest valid output.
Display
The result is rendered with syntax highlighting — keys, strings, numbers, booleans, and nulls each get distinct colors, making large payloads much easier to scan.
Common Use Cases
API Response Debugging
Paste raw API responses from curl, Postman, or browser DevTools to instantly read the structure. Collapsed, compact responses become scannable in one click.
Config File Editing
Format package.json, tsconfig.json, appsettings.json, and other config files to check their structure before committing — or minify them for production.
Log Inspection
Modern application logs are often JSON. Formatting a log line makes it easy to read nested error objects, trace IDs, and request metadata at a glance.
Pre-commit Validation
Quickly validate JSON before pushing to version control or deploying. Catches invisible issues like trailing commas or byte-order marks that would silently break a parser.
Data Sharing & Documentation
Pretty-print JSON to paste into wikis, tickets, or README files. Readable indented JSON communicates API contract examples far more clearly than a minified blob.
Bandwidth Optimization
Minify JSON for production APIs and CDN-cached responses. Even a 30% size reduction adds up when a response is served millions of times — always minify before serializing to storage.
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JSON Formatter — Pretty Print, Minify & Validate JSON Instantly
Learn how a JSON formatter works, what common JSON syntax errors look like, the difference between JSON and JavaScript objects, and how to format and validate JSON instantly with a free tool.
