The developer has effectively made the software for those using older hardware and operating systems.
Coriolis Systems (the developer) has ceased active development of iDefrag. As of recent updates: idefrag 211 license key link
Q: Can I use iDefrag on multiple computers? A: Yes, with a valid license key, you can use iDefrag on multiple computers. The developer has effectively made the software for
: If you specifically need legacy support for older macOS versions (10.6–10.9), you can find versions like 2.2.8 here. Compatibility Note with a valid license key