Your files stay on your Mac.
Opus is an open-source codec built for voice calls and streaming; AAC is the standard audio format for Apple devices, streaming services, and any player that handles .m4a or .mp4 containers. Converting Opus to AAC re-encodes the audio into a codec that iOS, macOS, iTunes, and services like YouTube accept natively. Convertessa runs the entire conversion on your Mac — no file is ever uploaded.
Drag one or more .opus files into Convertessa, or point the CLI at a folder. Every file stays on your Mac throughout the process.
Select AAC from the output format list. Because AAC is a lossy format, you can also set quality to balance audio fidelity against file size before converting.
Click Convert. Convertessa processes each file locally and writes .aac output alongside the originals — or to a destination folder you specify.
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 offline on your Mac. Your files never leave the device — there is no upload step and no server involved.
Yes. Drag the folder onto Convertessa or run convertessa ./folder --to aac in the terminal. Every .opus file in the folder is converted in one pass.
AAC is a lossy format, so Convertessa lets you set quality before converting. A higher setting preserves more audio detail at the cost of a larger file; a lower setting produces smaller files with some reduction in fidelity.