For basic solver, press the first button below which generates the search arrays to Depth 8. For better solver, press the second button to generate Depth 9 which takes longer initially but significantly improves search performance. Use of Dist Files eliminates generating the arrays, see Solver Help for details.

To use the Optimal Solver you will need to download five files (Dist1-4 & DistP2) as described in the above linked help page. To find optimal solutions the solver will need more time to run so the default Search Time is set to 60 (with no "s") which allows searching for up to 60 seconds. If search time is sufficient the solver will show "Optimal" under the Solve Log button after the solve completes, otherwise Search Time will need to be increased. The amount of time to find optimal solutions varies widely by both the cube configuration and the amount of computing horsepower your computer has so for a benchmark from which you can guesstimate your performance, a Ryzen 5 3.7 Ghz Quad-Core averaged under 15 seconds to find optimal solutions in a test of 1000 random cubes (for more info see section "Optimal Solutions" here).

Here are the same links with an example of how the cube display can be customized with URL parameters, see Help for details.