The Daily Sudoku X (SudokuWiki)

SudokuWiki.org is Andrew Stuart's long-running site about sudoku solving, built around his online solvers and strategy guides, and it publishes a set of numbered daily puzzles. The Daily Sudoku X is the diagonal variant: alongside the usual rules for rows, columns and 3x3 boxes, each of the two long diagonals must contain 1 to 9 exactly once. The diagonal cells are shaded so you can see them at a glance.

Each day's puzzle has a number and a date in its heading (#767 on 21 October 2026), with a star rating for difficulty. The free page gives one grade a day; All-Access Supporters can play all four. You enter digits straight into the grid with the keyboard or the on-screen number pad, keep pencil marks with Notes, and a timer runs beside the grid. A print version is linked above the puzzle.

The extra diagonal constraint gives you more to work with early on, so a Sudoku X often opens up faster than a plain sudoku of the same rating, and the site's Sudoku X solver can explain any step you get stuck on.

The page needs no account and works at phone size, where the grid fills the width of the screen. It suits sudoku players who want a regular daily variant with the same calm feel as the site's other dailies.