Your files stay on your Mac.
Convertessa re-encodes each MP3 into a FLAC file — a lossless, open container that stores the decoded audio without adding further compression artefacts. Processing runs entirely on your Mac; no file is ever uploaded. Convert a single track or a whole folder in one pass.
Drag one MP3 or an entire folder of tracks onto Convertessa. No file-size limit applies — everything is processed locally on your Mac.
Choose FLAC from the output format list. Convertessa will encode every queued file to the FLAC specification.
Click Convert. Convertessa writes a FLAC file alongside each source track. Your original MP3s are left untouched.
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. FLAC is a lossless container, so it stores the decoded MP3 audio without adding further compression artefacts — but it cannot recover detail discarded during the original MP3 encoding. The FLAC file is a bit-for-bit accurate copy of the decoded audio, not an upscale.
Never. Convertessa runs entirely offline. Your MP3 files are decoded and re-encoded on your machine; no data is sent to any server.
Yes. Drop an entire folder onto Convertessa or point the CLI at a directory: convertessa ./album/ --to flac. Every MP3 in the folder is converted in one pass.