Convert data files without handing them to a stranger.
Drop a file in, pick a format, get it back converted. Everything runs inside this page — your data never touches a server, because there is no server to touch.
- Real Parquet support. Read and write it in the browser, no Python needed.
- Options that matter. Delimiters, encodings, compression, sheets, nesting.
- No account, no paywall. Ads pay for it. Two animals benefit.
CSVParquet
Runs on your deviceOptions
Reading CSV
Auto-detect reads the first rows and picks the separator that splits them consistently.
Turn off when the file starts straight into data. Columns are then named column_1, column_2, and so on.
Turns "42" into a number and "true" into a boolean. Values with leading zeros stay text so IDs and zip codes survive.
Which worksheet to convert. Filled in once the workbook is read.
Dotted path to the array of records, such as data.items. Leave empty to use the whole document.
Turns {"user":{"id":7}} into a user.id column. Arrays are kept as JSON text.
Pick the encoding the file was written in. Wrong encoding shows up as garbled accents.
Comma-separated words that should become null instead of text.
Writing Parquet
Snappy is the default across Spark, DuckDB and pandas. Gzip is smaller but slower to read.
Turns a user.id column back into {"user":{"id":7}}.
Excel needs a byte order mark to open UTF-8 files with accents correctly.
Rows per row group. Larger groups compress better; smaller groups let readers skip more.
conversion-preroll
This short ad is what keeps the converter free.
Parquet is unreadable in a text editor. That is by design.Check your new Parquet file with ParquetReader — opens Parquet files directly.Pick your conversion
Each one has its own page with format-specific notes, options and answers. The converter above handles any pair, including ones without a dedicated page.
Private because of how it is built, not because we promise.
Most online converters upload your file, convert it on a server, and ask you to trust a privacy policy about what happens next. This one parses the file in a Web Worker on your own machine. There is no upload request to inspect, no temporary file on someone else's disk, and no retention period to wonder about.
It is also faster. A 50 MB CSV converts in the time an upload would still be negotiating TLS — and it works offline once the page has loaded.
Know what you are converting
CSV
Plain text rows that open anywhere, with no types and no schema.
Read the guide →Parquet
Typed, compressed, columnar storage built for analytical scans.
Read the guide →JSON
Nested, self-describing records that every language can read.
Read the guide →JSONL
One JSON object per line, built for streaming and appending.
Read the guide →Excel
Spreadsheet workbooks with sheets, formatting and cell types.
Read the guide →TSV
Like CSV, but tab-delimited, so commas inside values stay harmless.
Read the guide →Meet the reason this converter is free
This is Coconut and Whisky. Coconut is a peach Scottish Fold who supervises, which mostly means sitting on things and looking unimpressed. Whisky is a black Pomeranian who approves of everything immediately. Neither contributes to hosting costs. Both eat twice a day.
The converter runs entirely in your browser, so there are no per-conversion server costs — but there is still a domain, a build pipeline, and the work of keeping six file formats parsing correctly. The ads cover that. No account, no paywall, no upsell on the conversion itself, and no file ever leaves your machine.
Coconut has reviewed this arrangement and finds it acceptable.