Your files stay on your Mac.
Convertessa reads the audio track out of your FLV files and writes each one as an Apple M4A file (AAC inside an MPEG-4 container). Every step runs locally — your files never leave your Mac. Use the quality control to tune the AAC encoding level before you convert.
Drag one .flv file or an entire folder onto Convertessa. Every FLV file in the folder is queued automatically — no manual selection needed.
Choose Apple M4A from the output list. Set quality to control the AAC encoding level; higher quality produces a larger file.
Click Convert. Convertessa extracts the audio track from each FLV and writes an .m4a file beside the original. Nothing is uploaded — conversion happens entirely on 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.
Convertessa extracts the audio stream from each FLV and re-encodes it as AAC inside an M4A container. Use the quality slider to choose your target encoding level — a higher setting preserves more detail at the cost of a larger file.
Yes. Drop a folder onto Convertessa or run convertessa *.flv --to m4a in the terminal. Every .flv file in the folder is processed in one pass with no extra setup.
No. Convertessa runs entirely offline on your Mac. Your FLV files are never sent to a server or over the internet at any point during conversion.