JSON Formatter & Validator
Format, validate, minify, and inspect JSON with syntax highlighting. All processing is done locally in your browser.
How to format and validate JSON
You can upload a JSON file, reformat it with 2 spaces, 4 spaces, or tabs, minify it down to a compact single line, and copy the current editor contents. For valid objects and arrays, the tool shows an interactive tree; for other valid JSON (for example a string, number, boolean, or null), it shows the parsed value in monospace.
JSON formatter examples
- Format minified API responses with consistent indentation
- Validate copied webhook payloads before sending them downstream
- Minify JSON configuration files before embedding them in code
- Inspect parsed objects in a tree view when a raw JSON blob is hard to scan
What counts as valid JSON?
This formatter validates standard JSON according to RFC 8259. That means keys must be double-quoted, comments are rejected, and trailing commas are not allowed. When something is wrong, the editor highlights the exact spot and shows a message explaining what the parser expected instead.
Why valid JSON can still show warnings
Some JSON can be technically valid but still risky or surprising in practice. For example, duplicate object keys are allowed by many parsers, but downstream tools often keep only the last value and silently ignore the earlier ones.
When the formatter finds issues like duplicate keys, it keeps the JSON valid and editable, but shows a warning banner with line numbers and an amber squiggly underline so you can review those spots before copying or reformatting the document.
Where is the JSON processed?
Parsing, formatting, minifying, and tree rendering all happen locally in your browser after the page loads. This tool does not need a server round-trip to inspect or reformat the JSON you paste into the editor.