Your files stay on your Mac.
WebM is a container format that bundles video and audio into one file. Converting to MP3 extracts the audio track and encodes it as a standalone MP3, ready for any music player, podcast app, or media library. Because MP3 is lossy, you can set quality to balance file size against audio fidelity.
Drag in one WebM file or an entire folder. Convertessa processes every .webm it finds — no upload required, files stay on your Mac.
Pick MP3 from the output format list. Set quality to your preferred level — higher values keep more detail; lower values shrink the file.
Click Convert. Each WebM's audio track is extracted and saved as an MP3 alongside the original. Embedded metadata is stripped from the output file.
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. All processing happens locally on your Mac. Your files never leave your machine.
Yes. Drop the folder onto Convertessa or run convertessa ./folder/ --to mp3 in the terminal to batch-convert every WebM file inside.
For music or high-quality speech, choose a higher quality setting. For voice recordings or podcasts where file size matters more, a lower setting is usually sufficient. You can re-convert at any time if the result isn't what you expected.