Your files stay on your Mac.
Convertessa re-encodes your MP3 audio to the Opus format—an open, royalty-free codec that achieves better fidelity at smaller file sizes than MP3. Set a quality level to control the trade-off between detail and file size. Everything runs on your Mac; no files are uploaded.
Drag one MP3 or an entire folder into Convertessa. Batch mode processes every file in the folder in one pass.
Choose Opus from the output format list, then set the quality level to balance fidelity against file size.
Click Convert. Convertessa re-encodes each file locally and saves the Opus output alongside the originals.
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.
Opus typically achieves better audio fidelity than MP3 at equivalent file sizes, making it a practical choice when you want to reduce storage without audible quality loss.
Yes. Before converting, set the quality level in Convertessa. Higher values preserve more detail; lower values produce smaller files.
No. Convertessa runs entirely offline on your Mac. Your audio files are never sent to any server.