Your files stay on your Mac.
Convertessa reads the audio stream from your .mka container and re-encodes it as Opus, an open, royalty-free lossy codec optimised for speech and music at low file sizes. Set quality to balance fidelity against output size. Everything runs locally on your Mac — files never leave your machine.
Drag one .mka file or an entire folder into Convertessa. Batch mode processes every file in one pass.
Select Opus from the output format list, then adjust the quality slider to control the fidelity of the output.
Click Convert. Convertessa re-encodes each file offline 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 is a lossy codec, so some audio data is discarded during re-encoding. Use the quality setting to control how much — higher quality preserves more detail at the cost of a larger file.
Yes. Drop a folder onto Convertessa and it processes every .mka file inside in a single batch. You can also run convertessa /path/to/folder --to opus from the terminal.
No. Convertessa runs entirely offline. Your .mka files are read and written on your Mac — they never leave your machine.