How to solve this 8×8 logic puzzle

8×8 · steady · 17 steps

This 8×8 board rates as steady (difficulty score 843). Solving it from scratch takes 26 logical steps, using 7 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Paired regions, Shape squeeze. Every step below is forced — nothing here is a guess.

First, place a marker at row 8, column 1. Region has exactly one open cell left. Placing here clears the rest of row 8, column 1, and its region. Placing here also clears its 1 touching neighbour.
Next, every open cell left in this region sits in row 6, so its marker has to land there — clearing every other open cell in the row.
Then, every open cell left in this region sits in column 8, so its marker has to land there — clearing every other open cell in the column.
After that, every open cell in row 7 belongs to the same region, so that region's marker has to be somewhere in this row — clearing every other open cell in the region.
Now, together, two regions have open cells only in columns 2 and 3 — with one marker each, those two markers have to fill exactly those two columns, so every other region's open cells there can be cleared.
From there, every open cell left in this region sits in column 4, so its marker has to land there — clearing every other open cell in the column.
Following that, every remaining candidate in this region touches row 4, column 3 — so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
First, place a marker at row 6, column 3. Column 3 has exactly one open cell left. Placing here clears the rest of row 6, column 3, and its region. Placing here also clears its 2 touching neighbours.
Next, place a marker at row 4, column 2. Region has exactly one open cell left. Placing here clears the rest of row 4, column 2, and its region.
Then, place a marker at row 3, column 4. Region has exactly one open cell left. Placing here clears the rest of row 3, column 4, and its region. Placing here also clears its 1 touching neighbour.
After that, place a marker at row 5, column 8. Region has exactly one open cell left. Placing here clears the rest of row 5, column 8, and its region.
Now, every remaining candidate in this region touches row 1, column 6 — so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
From there, every open cell left in this region sits in column 7, so its marker has to land there — clearing every other open cell in the column.
Following that, every remaining candidate in this region touches row 2, column 6 — so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
First, place a marker at row 1, column 5. Region has exactly one open cell left. Placing here clears the rest of row 1, column 5, and its region.
Next, place a marker at row 2, column 7. Region has exactly one open cell left.
Finally, place a marker at row 7, column 6. Region has exactly one open cell left.

The key move here was Shape squeeze — once you can spot that, this board falls quickly. ∎