Your files stay on your Mac.
iTunes M4V is Apple's video container — the format used for movies and TV shows from the iTunes Store. Converting to WebM re-encodes the video with VP8 or VP9 and wraps it in an open, royalty-free container that plays natively in Chrome, Firefox, and Edge without plug-ins. Convertessa handles the entire conversion on your Mac; your files are never uploaded.
Drag one or more M4V files — or an entire folder — directly into Convertessa. The app queues every file and reads the source video and audio streams.
Choose WebM from the output format list. Because WebM uses lossy encoding, you can also set quality to balance visual detail against file size.
Click Convert. Convertessa re-encodes each queued file locally and saves the WebM output alongside the originals. Nothing leaves 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. WebM uses lossy compression, so Convertessa lets you set quality before converting. A higher quality setting preserves more detail at the cost of a larger file; a lower setting produces a smaller file with some visual loss.
Yes. Drop a folder onto Convertessa or run convertessa ./folder --to webm in Terminal to convert every M4V file inside in a single pass.
No. Convertessa runs entirely offline and processes files locally on your Mac. Your videos are never uploaded to any server.