About FlatNest β JSON Flattener & Unflattener
Free online tool to flatten nested JSON into dot-notation keys, or unflatten flat JSON back to nested objects. Runs locally in your browser with no upload and no signup.
FlatNest is a free, privacy-friendly JSON flattener and unflattener for developers, data analysts and anyone who works with APIs. Paste deeply nested JSON and instantly get flat dot-notation keys such as user.address.city, ready for CSV or spreadsheet export, Elasticsearch and OpenSearch mappings, feature-flag configs or side-by-side config diffs. Flip the switch to turn flat keys back into nested objects. Arrays are indexed, separators are configurable, and everything runs locally in your browser, so API responses and secrets never leave your machine. No account and no upload are required.
