Your files stay on your Mac.
Convertessa reads your WebM files and writes H.264/AAC MP4 containers directly on your Mac. No file ever leaves your machine. You set the output quality before conversion starts.
Drag one WebM file or an entire folder onto Convertessa. Every WebM file in the folder is queued automatically for batch conversion.
Choose MP4 from the output format list. Because MP4 uses lossy encoding, you can set quality before converting — adjust the quality slider to balance fidelity and file size.
Click Convert. Convertessa processes all files locally with no internet connection required. Your MP4 files appear in the same folder when done.
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 WebM files are read and written locally — nothing is sent to a server at any point.
Yes. Drop a folder onto Convertessa and every WebM file inside is queued automatically. From the command line: convertessa /path/to/folder --to mp4.
No. Convertessa preserves the original resolution of each WebM file. Only the container and codec change — the picture stays the same size.