Disk Drill 3.x is officially compatible with Mac OS X 10.8.5 and newer. It also supports macOS 10.12, 10.13 and 10.14.
The requirements for Disk Drill 2.x are simple. All you need is a Mac running OS 10.6.8 or later. It is fully compatible with Yosemite (10.10) and EL Capitan (10.11), however with the release of Disk Drill 3 it’s deprecated.
If you are interested in running Disk Drill on an older Mac, you can download a copy of Disk Drill 1.8, which is available on demand for Mac OS 10.5 — 10.6.7.