... by: Yves

There are 879 two cells trivial solutions in this #718

one is J8=9 & F9=6

... by: Dieter

#718 - initially populated cells: 21 = 25,9 %
No solver used, solver = brain.
basics: %

Strategy: numbers 1,3,5,7 occur most frequently, combine two cells with almost same candidates.
combinations of D8 = (1,3,5,6) and D9 = (3,5,6,7,8);
after basic checks 4 matrices left: 3/5, 3/7, 5/7 and 6/5.
D8=5 & D9=7 solve with J1=5.

Optimization:
D8=5 & J1=5 or D9=7 & J1=5 solve.

... by: Serban

# 718 Basics to 21

1. G4 = A6 = 5 solve

2. E7=9 & F7=8 solve

3. F6=9 & F7=8 solve

... by: Norman Powell

This puzzle is solved on the fourth pass of Forcing Networks, which finds the solution when checking to a possibility..
AS's Solver Opens in the same way and finds 6 eliminations through Forcing Networks before running out of strategies, indicated [AS# order of discovery below]. My implementation reports eliminations as they are found. AS reports in order of increasing length of post-hoc inference chain that would reveal elimination.
Here are the details:
Hidden Pair: Column 9 for Values 5, 7 in Cells B9 & D9, removing other possibilities from those cells. [As AS]
Confined to Box: Value 3 is confined to Column 8 and Box 6, removing other 6s from Column 8.
Forcing Network First Pass: Eliminate the follow since they produce contradictions when ON:
2D1[AS#3], 1D8, 8E5[AS#5], 1F1, 6F6, 8F6 [AS#1], 9F7[AS#6], 4G2[AS#4], 8J4[AS#2].
Forcing Networks Second Pass: Eliminate the follow since they produce contradictions when ON:
2C1, 6D1, 6D3, 6D8, 2J1, 4J9.
Confined to Box: Value 6 in Row 4 and Box 5.
Forcing Networks Third Pass: Eliminate the follow since they produce contradictions when ON:
8A6, 6C1, 4C4, 2D3, 7D4, 8D4, 8D6, 9E8, 2F2, 2F6, 2G2
Hidden Single: in Row F, F1=2.
Confined to Box: Value 8 is confined to Column 6 and Box 8.
3D Medusa: Rule 5 1C5 can see both colours, eliminate.
Forcing Networks Fourth Pass: Eliminate the follow since they produce contradictions when ON:
7A1, 9A3
However the solution is found when testing 88A4 for being ON.
Solver VBA in Excel [inspired by AS's Solver and Sudoku Wiki], with lots of graphical cues, so very slow:
2:57 [min:ss]
Forcing Networks gradually moving up the methods for efficiency, eclipsing X-Cycles, AIC, Grouped X-Cycles and Grouped AIC. Almost Locked Sets after Forcing Networks and is still triggered by some examples that get past Forcing Networks.