Your files stay on your Mac.
Converting an Excel 97–2003 file to CSV extracts the spreadsheet data into plain, comma-separated text — no proprietary binary encoding, no formatting overhead. The result is a flat text file that scripts, databases, and data pipelines can parse without any special library. Everything runs on your Mac; files are never uploaded.
Drag one XLS file or an entire folder into Convertessa. Batch mode processes every XLS in the folder in one pass.
Select CSV from the output format list to tell Convertessa what to produce.
Click Convert. Convertessa reads each XLS locally and writes the CSV output to your chosen destination — no internet connection 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 on your Mac. Every XLS file is read and written locally — nothing leaves your machine.
Yes. Drop a folder onto Convertessa or pass a directory path to the CLI and every XLS file inside is converted to CSV in one pass.
CSV is a plain-text format that stores cell values only. Formulas are represented by their last computed result, and visual formatting such as colours, fonts, and borders is not carried over to the output file.