JSONFormatter.org does considerably more than this tool: format conversion (JSON to XML/CSV/YAML/TSV/Base64 and back), a tree/graph view, file upload and download, and code generation to half a dozen languages. If you need any of that, it's the more complete tool and this page won't pretend it isn't.
What this page offers for the common case — paste JSON, format it, validate it, minify it, pull one value out with a path query — is the same core result without ads, and alongside regex/JWT/cron/hash tools rather than as a standalone site.
Need format conversion, file handling, or code generation from JSON: JSONFormatter.org. Just need to format, validate, or query a JSON document quickly: this tool.