Your files stay on your Mac.
Converting WebM to Apple M4A extracts the audio stream from the container and re-encodes it as AAC inside an M4A file ready for iTunes, QuickTime, and any AAC-compatible player. The video track is dropped—you get a lean audio file and nothing else. Conversion runs entirely on your Mac; your files never leave the machine.
Drag one WebM file or an entire folder onto Convertessa. All valid WebM files are queued automatically.
Pick Apple M4A from the output format list. Adjust the quality slider if you want to balance file size against audio fidelity.
Click Convert. Convertessa extracts each audio stream and writes an M4A file alongside the original—no upload, no waiting for a server.
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.
It is discarded. Convertessa reads the audio stream from the WebM container and writes it to an Apple M4A file. The resulting file contains audio only.
Yes. Because M4A uses lossy AAC encoding, Convertessa lets you set the quality level before converting. Higher quality produces a larger file; lower quality reduces size at the cost of some fidelity.
Yes. When you drop a folder or pass a directory path to the CLI, Convertessa recurses into sub-folders and converts every WebM file it finds.