flatten nested JSON to clean columns, free and in your browser

Paste or drop JSON or NDJSON with nested objects and arrays and get a flat table: user.address.city style columns, arrays unrolled, mixed shapes reconciled. Preview the first thousand rows instantly, then export the whole file - streaming, so gigabyte NDJSON logs work too.

how to use it

1. Drop or paste a .json or .ndjson file. Nested values arrive as a json column rather than being flattened behind your back.
2. Click that column's header and choose flatten json - or add the step from the pipeline panel.
3. Tick the keys you want as columns. "all leaves" takes everything; leave a branch unticked and it stays as JSON text.
4. Export csv. The whole file streams through, so there is no row limit.

• Handles objects in arrays, arrays in objects, and ragged records that only sometimes have a key.
• Finds the records inside an envelope: {"data": [...]} or a nested API response loads as the table, not as one wide row - and every other array in the document is one click away.
• Paste JSON straight from your clipboard, pretty-printed or minified, single document or one object per line.
• Columns still holding a JSON blob get a click to flatten prompt with the discovered paths already selected.
• Choose exactly which columns survive: rename, drop, reorder before export.
• Export CSV, JSON, NDJSON, SQL inserts, or load the result into the built-in SQLite engine.
• Full-file column profiles: distincts, top values, null share - from every row, not a sample.

every tool in the box

• data workbench - profile, clean, transform, and export CSV, JSON, and SQLite - the full suite
• JSON flattener - nested JSON or NDJSON to flat columns, arrays and objects unrolled (this page)
• CSV PII scrubber - find emails, phones, SSNs, and card numbers - mask, hash, or drop them
• JSON to CSV - convert JSON or NDJSON to CSV with full column control
• CSV to JSON - convert CSV to JSON or NDJSON, streamed at any size
• Excel to CSV - read .xlsx workbooks and export CSV, sheets and all
• CSV to Excel - write a real .xlsx where leading zeros and dates survive
• SQL on CSV - real SQL over your files: joins, GROUP BY, a read-only console
• CSV to SQLite - drop several files, get one .sqlite database with discovered foreign keys
• CSV to SQL - CREATE TABLE and INSERT statements for Postgres, MySQL, SQL Server, SQLite
• JSON to TypeScript - TypeScript interfaces and JSON Schema derived from your real data
• large CSV viewer - open files past Excel's 1,048,576-row limit without loading them into RAM
• regex painter - highlight example matches, get a verified regular expression back
• encoding fixer - detect windows-1252/UTF-16 and repair garbled text (José → José)
• log parser - read log files as events: layouts detected, stack traces kept whole, timestamps normalized, and a volume-over-time strip drawn in SQL across every row
• visualize - chart any table you have open - bar, line, area or point - drag across it to filter, and export svg, png, or the vega-lite spec that drew it
• theme builder - design, test, and export custom color themes with live previews, palette derivation, and contrast diagnostics

Like every unfckr tool, this runs 100% in your browser: no upload, no servers, no signup, no analytics. A Content-Security-Policy header blocks every programmatic network channel, so not even malicious code could phone home - and you can watch it happen: the privacy page runs six live escape attempts and shows the browser refusing each one.

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