How to use the Offline CSV Converter (Desktop App)
Convert JSON, CSV, Parquet and Excel – one file or a whole folder.
The Format Converter moves data between JSON, CSV, Parquet and Excel without code or an install. It reads your file in the browser, flattens nested JSON into columns, keeps or guesses column types, and writes the format you choose. Use it to open API data in Excel, load a spreadsheet into an app, shrink a big CSV into Parquet, or look inside a Parquet file. Nothing is uploaded, so it is safe for customer and business data.
Pick From and To
Drop or paste your data
Convert and download
Tips
Use the Batch / Folder tab to convert many files into one ZIP.
Nested JSON becomes columns like address.city.
Excel: the first sheet is read; old .xls files are not supported.
Yes. Install Data Utility from the sidebar button in Chrome or Edge. Tools that run on your device, such as converting, joining and masking, keep working without internet. AI tools and API calls need a connection.
How big can a file be?
It depends on your device. A few hundred MB usually works.
Which conversions does the Format Converter support?
Any direction between JSON, CSV, Parquet and Excel (.xlsx), for one file or a whole folder. Nested JSON is flattened into columns such as address.city. For Excel, the first sheet is read; old .xls files are not supported.
Why did my number or date change after converting?
Types are detected from the values. Turn off "Detect types" to keep everything as text, which also keeps leading zeros in IDs and phone numbers.
Related pages
JSON, CSV, Parquet and Excel Converter: Convert between JSON, CSV, Parquet and Excel online for free, one file or a whole folder. It runs in your browser, so nothing is uploaded.
JSON to CSV Converter: Convert JSON to CSV online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
CSV to JSON Converter: Convert CSV to JSON online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
CSV to Parquet Converter: Convert CSV to Parquet online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
JSON to Parquet Converter: Convert JSON to Parquet online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
Parquet to CSV Converter: Convert Parquet to CSV online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
Parquet to JSON Converter: Convert Parquet to JSON online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.
CSV to Excel Converter: Convert CSV to Excel online for free. Drop a file or paste data, click convert and download. It runs in your browser, so your data is never uploaded.