JSON Formatter

Yes, it validates as it formats. When you paste in JSON, the tool runs it through a parser and if anything is off, like a missing comma, a trailing comma that strict JSON does not allow, unquoted keys, or mismatched brackets, it will flag the exact issue so you can fix it. I find this honestly more useful than the formatting itself because tracking down a syntax error in a 500-line JSON response by eyeballing it is painful. Tools like JSONLint do validation too, but here you get validation and pretty-printing in one step without switching tabs. One thing to note: this is strict JSON validation, so if you are working with JSON5 or JSONC (JSON with comments), those will show as errors since they are technically not valid JSON. For those formats, you would want a JSON5-specific parser.

Yes, you can paste or type JSON up to 500 KB, which covers the vast majority of real-world use cases. That is roughly the size of a large API response, a chunky config file, or a decent-sized data export. Everything runs in your browser using JavaScript's built-in JSON.parse and then re-serializes with proper indentation, so performance depends on your machine, but modern browsers handle 500 KB of JSON in milliseconds. If you are working with truly massive JSON files in the multi-megabyte range, you are probably better off using a desktop tool like jq on the command line or the JSON formatter built into VS Code. But for quick formatting of API responses, webhook payloads, or config files you grabbed from somewhere, this handles it easily. Just paste it in and you will get clean, two-space-indented output instantly.