Your files stay on your Mac.
Converting a WebM file to Matroska Audio (.mka) pulls the audio track out of the WebM container and re-encodes it into a Matroska Audio file — no video data carried over, just the sound. You control output quality before converting. Files never leave your Mac.
Drag one WebM file or an entire folder onto Convertessa. Batch mode queues every file in one pass.
Choose Matroska (.mka) from the output list. Set quality to balance file size against audio fidelity.
Click Convert. Convertessa writes .mka files alongside your originals — no upload, no cloud, conversion runs entirely 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.
Yes. Convertessa decodes the audio stream from the WebM container and re-encodes it inside the .mka container. Use the quality setting to control the trade-off between file size and fidelity.
No. Convertessa strips embedded metadata during conversion, so the resulting .mka file contains no identifying tags from the source WebM.
Yes. Drop a folder onto Convertessa or run convertessa ./folder --to mka in the terminal. Every WebM file in that folder is converted in a single batch.