Your files stay on your Mac.
Convertessa decodes WMV — VC-1 or older Microsoft video with WMA audio inside an ASF container — using FFmpeg, and writes a standard H.264 and AAC MP4 your Mac can actually open. It all runs offline, so an archive of internal training footage or family tapes never goes anywhere. Point it at a folder, set quality once, and let the queue grind through the backlog.
Double-click a .wmv on a current Mac and nothing useful happens. That is not a fault in your machine, it is the end of a long story. A .wmv is an ASF container holding Microsoft's own codecs: WMV7 and WMV8, which are Microsoft's take on MPEG-4 Part 2, or WMV9, which was later standardised as VC-1. The audio is almost always WMA. Apple never shipped decoders for any of it — playback came from Flip4Mac's Windows Media Components for QuickTime, and that route died along with QuickTime 7 and 32-bit apps.
So the .wmv files that surface tend to be old: camcorder transfers, Windows Movie Maker exports, corporate training modules, mid-2000s screen captures, media pulled out of a legacy PowerPoint deck, footage off an office security recorder. FFmpeg still decodes all of it, and Convertessa writes H.264 with AAC audio into an MP4 — the pairing Photos, QuickTime, Final Cut and every iPhone accept without argument.
Some WMV files are wrapped in Windows Media DRM, bought from a store that no longer exists or issued by a company's old media server. The video inside is encrypted, no key lives on your Mac, and the conversion stops rather than emitting a scrambled file. Nothing on-device can open those.
Drag your .wmv files, or the entire folder you copied off the Windows machine, onto the queue. FFmpeg does the decoding, so files QuickTime cannot even preview are read without complaint.
Pick MP4 as the target. The quality setting decides how hard H.264 works on footage an old Microsoft codec already compressed once, so a notch higher than usual pays off on grainy tape transfers.
Start the queue and leave it. Every file is re-encoded locally and written beside its source or into the folder you name, while the originals stay untouched as your archive copy.
Images, audio, video, documents, archives, eBooks and fonts — 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.
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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.
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New formats, new features, and fixes — every release, on the record.
Because macOS has never contained a Windows Media decoder. For years the gap was filled by Flip4Mac, a plug-in that taught QuickTime 7 to read ASF; Telestream retired the free component, and macOS Catalina removed 32-bit support and QuickTime 7 with it. Nothing replaced it. That is why a .wmv shows a generic icon and a grey screen, while the same file plays fine on any Windows PC from the last twenty years.
VLC bundles its own decoders and plays nearly anything, but nothing else on your Mac borrows them. Final Cut Pro, iMovie, Photos, Keynote, Messages and iOS all want H.264 or HEVC in an MP4. Convert when the footage has to be edited, imported into a library, dropped into a presentation, or sent to someone. If it only ever gets watched in VLC, leave it alone.
That is interlacing, and it came with the source. Old camcorders recorded two half-height fields per frame at slightly different moments; on a progressive display the two halves show as combing on movement. Those fields are part of the picture data, so they are still there in the MP4. Some players smooth it on playback, most do not. The MP4 is an honest copy of what the WMV held.
It is almost certainly wrapped in Windows Media DRM. The video stream is encrypted and the licence lived on a server that has probably been switched off for a decade, so there is no key on your machine and FFmpeg has nothing it can decode. Convertessa stops rather than writing a broken file. Files ripped or exported by you personally are unprotected and convert normally.
No. Re-encoding cannot invent detail an old codec already discarded, and a 320x240 clip from 2004 will still be a small, soft clip afterwards. What the quality setting controls is how much of the existing detail is preserved through this second pass. Set it generously and the MP4 is visually indistinguishable from the WMV; set it low and you will see blocking on top of the original softness.
Use the CLI and let it run overnight. One file: convertessa lecture.wmv --to mp4. A whole archive into a separate destination, with quality raised for tape footage: convertessa ~/OldDrive/*.wmv --to mp4 --quality 85 -o ~/Converted. Nested folders are handled by pointing at the directory itself. Nothing is deleted, so the source drive stays exactly as you found it.
Effectively, yes — ASF is the container, and .wmv is the name Microsoft gave it when it holds Windows Media video. A .asf may hold the same VC-1 or WMV9 stream, and .wma is the audio-only sibling. Renaming the extension changes nothing about what is inside. If a file plays as video on Windows but not on your Mac, this conversion is the same fix regardless of which of those three extensions it wears.