JSON Formatter

How to format and validate JSON?

Formatting and validating JSON is quick: Paste your JSON code into the input box — it can be a single object, array, or nested structure. The tool validates your JSON in real-time as you type, highlighting any syntax errors with the exact line number and character position. If the JSON is valid, click 'Format' to apply pretty-printing with consistent indentation (choose 2 or 4 spaces). Click 'Minify' to compress the JSON into a single line by removing all whitespace — useful for reducing payload size in API responses. Click 'Sort Keys' to alphabetically reorder object properties, which helps with diff comparisons and deterministic output. Copy the formatted or minified result and paste it into your code editor, API client, or configuration file.

Common JSON syntax errors and how to fix them

JSON has strict syntax rules that differ from JavaScript object literals. The most frequent error is trailing commas — JSON arrays and objects cannot end with a comma after the last element. Single quotes are invalid in JSON; all strings must use double quotes. Comments (// or /* */) are not allowed in JSON, unlike JavaScript. The values true, false, and null must be lowercase — True, False, and NULL will cause parse errors. Undefined is not a valid JSON value; use null instead. Keys must always be quoted strings — {name: 'value'} is invalid, {'name': 'value'} is invalid, but {"name": "value"} is correct. Special characters in string values must be escaped: use \\n for newlines, \\t for tabs, \\/ for forward slashes, and \\uXXXX for Unicode characters. When working with API responses, tools like Postman and Insomnia automatically format JSON, but manual editing requires attention to these rules. Our validator catches all these errors and reports the exact location for quick fixes.

JSON formatting strategies for different workflows

Different development scenarios benefit from different formatting approaches. During debugging, use formatted JSON with 2-space indentation and sorted keys — sorted keys make it easier to spot differences between two JSON outputs using visual diff tools. For API documentation, format with 4-space indentation and preserve the original key order to match the API specification exactly. For production payloads, minify JSON to reduce bandwidth — a typical API response of 5KB formatted may shrink to 3.5KB minified, saving 30% on network transfer. For configuration files (package.json, tsconfig.json, docker-compose.yml alternatives), use 2-space indentation as it's the community convention and keeps deeply nested configs readable. When working with large JSON files (>1MB), consider streaming parsers instead of loading everything into memory. Our tool handles files up to several megabytes efficiently, but for very large datasets, command-line tools like jq or python -m json.tool are more appropriate.