Your files stay on your Mac.
Kindle AZW3 (Format 8) embeds advanced HTML5 and CSS3 layout features that older Kindle hardware and many third-party e-readers cannot render. Converting to MOBI produces a file that opens on every Kindle generation and any app that supports the format. Convertessa handles the entire conversion locally on your Mac — your library never leaves the machine.
Drag a single AZW3 book or an entire folder onto Convertessa. Batch mode queues every file and converts them in one pass.
Choose Kindle MOBI from the output format list. Because MOBI is a lossy target, you can also set quality to balance file size against formatting fidelity.
Hit Convert. Convertessa writes the MOBI files alongside your originals — or to any folder you specify — without touching a remote server.
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. MOBI is the format supported by every Kindle generation, including the earliest hardware models. AZW3 introduced layout features those devices cannot parse; converting strips the AZW3-specific markup and produces a file the device can open without issue.
Yes. Drop a folder onto Convertessa or run convertessa ./library/ --to mobi from the terminal. Every AZW3 file in the folder is converted in a single batch and the MOBI files appear in the same location.
No. Convertessa runs entirely offline on your Mac. Your AZW3 files are never sent to a server — the conversion happens locally and your library stays private.