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DataFlattener

In-browser tool for CSV exports with JSON payload columns

CSV JSON Column Expander

Turn a column of raw JSON into flat columns, right next to it. Streams large files with zero uploads.

100% Client-Side

Step 1 of 3: Source file

Step 01 / Source file

Choose your file

Streams from disk

Drop a .csv, .tsv, or .txt file here (Handles 2GB+ natively)

or browse your files • one file at a time

Architecture specification

Engineered for multi-million-row workloads

JSON Columns Found for You

The first rows are sampled and any column whose cells are JSON objects or arrays is selected. Pick more, drop some, or keep the raw JSON next to the new columns.

Automatic detection

Real CSV, Any Size

Quoted fields, doubled quotes and line breaks inside cells are handled like a spreadsheet does. A fast pass finds safe row boundaries so parallel workers can stream multi-gigabyte files.

RFC 4180 parsing

Zero Cloud Ingestion

Pure sandbox isolation: your data never goes over the network, and a strict Content-Security-Policy blocks every other site. The page only ever sends a feedback message you choose to write. Your data stays inside your own SOC 2, HIPAA and GDPR boundary.

No uploads, no telemetry