Your files stay on your Mac.
Convertessa pulls the audio track out of your Matroska MKV container and writes it as an AU file — Sun's original audio format used in Unix and Java environments. The conversion runs entirely on your Mac; your files never touch a server. Drop a single clip or an entire folder and convert in one pass.
Drag one MKV file or a whole folder of them onto Convertessa. The app reads the audio stream directly from the Matroska container.
Pick AU from the output list. Convertessa will extract the audio track and write it as an AU file.
Click Convert. Your AU files appear alongside the originals. No upload, no waiting on a server — everything runs offline on your Mac.
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.
AU (Sun audio) is a simple audio file format developed by Sun Microsystems. It stores PCM audio and is natively supported in Unix systems and Java's javax.sound API, making it a useful interchange format for those environments.
Yes. Convertessa converts files locally — nothing is uploaded to a server. The AU output is written directly to your disk, and your source MKV files are never transmitted anywhere.
Yes. Drop a folder onto Convertessa or use the CLI: convertessa /path/to/folder --to au. Every MKV file in that directory is converted to AU in one pass.