Platinum Blonde Sudoku — Play It Online, With the Full Solution

Updated 15 October 2026

Platinum Blonde is a 21-clue sudoku built specifically to push the Sudoku Explainer scale, and it is commonly rated around SE 10.9 — above AI Escargot, below Everest and Golden Nugget. Its givens run in a band from the top-right corner to the bottom-left, so the opening looks deceptively open. Play it below, print it, or read the engine’s solution.

Clues

21

Published SE rating

SE 10.9

Suuudokuuu rater

8.5+, past every implemented technique

Play Platinum Blonde in the appPrint Platinum Blonde — PDF with the solution

Where Platinum Blonde comes from

Platinum Blonde comes from the era when solvers raced to find grids that defeated every named technique. Rather than being designed around a pattern a human would recognise, it was found by searching for resistance to logic, and the difficulty only shows once ordinary subsets and fish run out and the solve has to fall back on chains and nets that span the whole board.

Source: sci.math, “Platinum Blonde”. The SE figure is the published rating the Infinity corpus carries, not a Suuudokuuu measurement. The other record grids are on the hardest sudoku puzzles page.

The Platinum Blonde solution, step by step

Suuudokuuu’s source-available engine solves Platinum Blonde in 106 steps, reaching for the cheapest technique that still makes progress, exactly as it does when it rates a puzzle. 14 of those steps are forcing chains: the engine assumes a candidate, follows its consequences until something breaks, and removes the assumption. At 2 points even that runs dry — no technique the engine implements moves the grid — and the walkthrough says so, fills the cell with the fewest candidates from the verified solution, and carries on with logic from there. Every other step is a named deduction you can check by hand.

Along the way the walkthrough uses Full House, Naked Single, Hidden Single, Pointing Pair, Box Line Reduction, Naked Pair, Hidden Pair, Finned Swordfish, Sashimi X-Wing, XY-Chain, AIC and Nishio Forcing Chain.