Your files stay on your Mac.
Converting Excel 97–2003 (.xls) files to Excel Workbook (.xlsx) repacks the old binary format into the Open XML structure used by Excel 2007 and later. The result is smaller, more portable files that open cleanly in current versions of Excel, Numbers, and Google Sheets. Convertessa runs every conversion on your Mac — your spreadsheet data never leaves the machine.
Drag one .xls file or an entire folder of them onto Convertessa. Batch mode processes every spreadsheet in a single pass.
Pick Excel Workbook (.xlsx) from the output list. The target format is always your choice — Convertessa never guesses.
Click Convert. Your .xlsx files land beside the originals, ready to open in any modern spreadsheet app.
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.
Yes. Convertessa repacks the spreadsheet's binary data into Open XML without altering cell values, formulas, or formatting. What you had in the .xls file is what you get in the .xlsx file.
Yes — drag an entire folder onto Convertessa and every .xls file inside is converted in one batch. From the CLI, run convertessa *.xls --to xlsx to target multiple files in one command.
No. Convertessa runs entirely offline on your Mac. Your files are never uploaded, streamed, or sent to any server — the conversion happens locally on your machine.