What Is JSON? A Complete Developer Guide
JSON is the lingua franca of modern APIs. This guide covers its syntax, data types, common use cases, and how it compares to XML and YAML.
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JSON Formatter & Validator
Format, validate, minify and convert JSON
Free online JSON formatter, validator and minifier. Beautify or compress JSON with syntax highlighting, error detection, indentation control and JSON-to-YAML conversion — all processed locally in WebAssembly. No data leaves your browser.
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// quick guide
JSON (JavaScript Object Notation) is the universal data interchange format of the web. Nearly every public REST API returns JSON, every modern configuration file uses it, and every database with a JSON column stores it. Despite its ubiquity, raw JSON from APIs or logs is often minified into a single unreadable line, or contains subtle syntax errors that cause cryptic parse failures.
This formatter solves both problems. It parses the JSON, reports exactly what is wrong if it is invalid, and renders the output in whichever view makes it easiest to understand: indented text, a compressed single line, or an interactive collapsible tree.
How to use this tool:
- Paste your raw JSON text into the left input panel. The tool starts validating immediately as you type.
- If the JSON is valid, a green indicator appears. If it is invalid, the error message shows the exact line and column of the problem, plus a description of what the parser expected to find.
- Use the Format button to beautify with indentation and syntax highlighting. Use Minify to strip all whitespace for compact storage or transmission. Use Tree for a collapsible node-by-node view of the structure.
- Adjust the indentation size between 2 and 4 spaces depending on your project's code style. Enable Sort keys to normalize key order, which makes comparing two JSON objects side-by-side much easier.
- Click the copy icon to copy the result to the clipboard, or download it as a
.jsonfile.
Common JSON syntax mistakes: The two most frequent errors are trailing commas (e.g., {"a": 1,}) and single-quoted strings ({'key': 'value'}). Both are valid in JavaScript but invalid in strict JSON. The validator catches these instantly.
All processing happens locally in your browser using a WebAssembly-compiled parser — no network requests are made, making this tool safe for JSON that contains API keys, auth tokens, or other sensitive configuration.
// frequently asked questions
What is a JSON Formatter & Validator?
A JSON Formatter and Validator is a utility that parses a raw JSON string, checks if it conforms to JSON specifications, highlights any formatting errors, and beautifies it with indentation and syntax highlighting for human readability.
Is my data secure when using this JSON formatter?
Yes, 100% secure. Unlike other online utilities that upload your data to a remote server, FormatMaster processes all your JSON locally inside your browser using WebAssembly. No inputs, keys, or configurations are sent to any server.
Can I format JSON without an internet connection?
Absolutely. Since all formatting and parsing operations run locally in your web browser, once the page has loaded, you can disconnect from the internet and keep using the tool without any issues.
What happens if my JSON is invalid?
The validator will show a red 'Error' indicator. It will point out the exact line and column number of the syntax error and describe what was expected (e.g., missing comma, unclosed quote) to help you fix it quickly.
Can I convert JSON to YAML with this tool?
Yes. The formatter includes a JSON-to-YAML conversion mode. YAML is a superset of JSON that is often more readable for configuration files. The conversion preserves all data types and nesting levels.