Your files stay on your Mac.
CSV is plain text: one row per line, values separated by commas. Convertessa reads each file, maps its columns and rows into a structured worksheet, and writes a .xlsx file that opens natively in Microsoft Excel, Numbers, or LibreOffice Calc. Every step runs locally on your Mac — no file is ever sent to a server.
Drag one CSV file or an entire folder into Convertessa. You can add as many files as you need in a single batch.
Select Excel Workbook (.xlsx) from the output format list. Convertessa will write one .xlsx file for each CSV you dropped.
Click Convert. Each CSV becomes a .xlsx file with its columns and rows intact, saved alongside the originals. No upload required.
Images, audio, video, documents, archives and eBooks — all converted natively, right on your Mac.
Pick a format you have — see everything Convertessa can turn it into.
Convert hundreds of files at once with per-type group defaults and individual overrides.
First-class support for HEIC, AVIF and WebP — encode and decode, both ways. Read JPEG XL and a dozen more modern formats too.
Drop files anywhere on the window. Native, instant, and exactly what you’d expect on a Mac.
Dial in compression, resolution and bitrate. Keep originals pristine or shrink for sharing.
Never overwrite a file by accident. Convertessa appends safe suffixes automatically.
Every job is logged locally. Re-run a previous conversion or revisit recent outputs in a click.
Bundle your converted files straight into a single ZIP, TAR or 7z — packaged and ready to share the moment a job finishes.
Right-click any file in Finder and choose Convert. A Quick Action handles it on the spot — no need to open the app first.
Shrink Convertessa to a tidy mini window that tucks into a corner — just a drop zone and a format picker for quick, one-off conversions.
No cloud. No account. No upload. Every conversion happens entirely on-device, using the power already in your Mac. What you convert is nobody’s business but yours.
Script conversions, wire them into your build, or batch a folder from the terminal. The same engine, no GUI required.
Read the full CLI documentation →Shrink Convertessa down to a small, focused window — drop, convert, done, with your recent conversions one click away.
macOS 14+ · Apple Silicon & Intel
New formats, new features, and fixes — every release, on the record.
No. Convertessa runs entirely offline. Your files are read from disk and written back to disk — nothing is uploaded to any server at any point.
Yes. Drag a folder onto Convertessa or use the CLI with a wildcard (convertessa *.csv --to xlsx) to batch-convert every CSV file in one pass.
Each .xlsx file contains one worksheet with the same columns and rows as the source CSV, ready to open in Microsoft Excel, Numbers, or LibreOffice Calc.