JSON Formatter & Validator — Free Beautifier

Three JSON errors kill parsing instantly

JavaScript is lenient about syntax. You can write {name:"John",age:30,} and it runs. JSON is unforgiving. A trailing comma after the last property fails immediately: {"name":"John","age":30,} produces Unexpected token } in JSON at position 47. Single quotes instead of double quotes break it: {'name':'John'} fails the same way. Unquoted keys fail too: {name:"John"} is valid JavaScript but invalid JSON—it must be {"name":"John"}. The error message gives you the byte position but not the cause. For a 10KB config file, position 4500 means you know the general area, but searching nearby for trailing commas or quote mismatches takes manual work.

This formatter catches all three and shows the position

Paste any of those invalid snippets and press Validate: it reports the error in red, citing the exact position where JSON.parse() failed. Beautify reformats valid JSON with fixed 2-space indentation—useful for reading large config files. Minify strips every space and line break, so a pretty-printed object spread over five indented lines collapses to the single line {"name":"John","age":30}. Across a large API payload that whitespace is real bandwidth. All three operations parse first: if your input is invalid, none of them produce output.

What this tool does not do

No JSON5 support: no trailing commas, no comments, no single quotes. No NDJSON (newline-delimited JSON for streaming). No custom indentation levels—you get 2 spaces, fixed. No key sorting. If you need a custom indent, use your editor's built-in formatter. For comment-heavy files, strip the comments first or use a JSON5 parser. For megabyte-scale files this browser tool will slow down; reach for a command-line tool such as jq instead. For pattern matching across text rather than structure, see the Regex Tester, or the Markdown Editor for prose.