K.O. Sudoku - Sudoku Solver

Various types sudoku puzzles, answers, step-by-step explanations, allow take photo to input.
It supports 3/4/5/6/7/8/9/10/12/15/16 grid sudoku, irregular sudoku, killer sudoku, kendoku, skyscraper sudoku, snow sudoku, necklace sudoku, thermo sudoku
, arrow sudoku, clone sudoku, blackout sudoku, odd/even sudoku, palindrome sudoku, little killer sudoku, direction sudoku, outside sudoku, sum frame sudoku, OEBS sudoku, 3D sudoku, cube sudoku, samurai sudoku, flower sudoku, windmill sudoku, gattai sudoku, butterfly sudoku, cross sudoku, twodoku, triple doku, sohei sudoku, snow sudoku, inequality sudoku, fortress sudoku, odd-even minesweeper sudoku, slanted-lines sudoku, kropki sudoku, product sudoku, ratio sudoku, addition sudoku, VX sudoku, 56 sudoku, battenburg sudoku, quad max sudoku, exclusion sudoku, odd-even lines sudoku, anti-diagonal sudoku, consec-ineq sudoku, BMS sudoku, big-small sudoku, odd sudoku, even sudoku, connected irregular sudoku, add/sub sudoku, balanced sudoku, consecutive sudoku, non-consecutive sudoku, touchless sudoku, anti-knight sudoku, anti-bishop sudoku, diagonal sudoku, percent sudoku, window sudoku, asterisk sudoku, girandola sudoku, center dot sudoku, pyramid sudoku, offset sudoku, letter-map sudoku, etc.
There are also technique tutorials and a rich online sudoku store.
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K.O. mode: Provide the solution directly.
Help mode: Provide step-by-step explanations.
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Sudoku Rules: Fill in the 9x9 grid with numbers 1~9 such that each row, column, and 3x3 box contains each number exactly once.
Irregular Sudoku: Each row, column, and irregularly shaped box contains no repeating digits.
Killer Sudoku: Combines classic Sudoku rules with "killer cages" (dashed-line groups). Each cage shows a sum for its digits, which must also be unique within the cage.
Kendoku (Newdoku/Calcudoku/Mathdoku): Fill an n x n grid with digits 1-n (no repeats per row/column). Groups marked by thick lines show a target number and operation (+, -, ×, ÷) that their digits must satisfy. If no operator is given, any operation applies.
Skyscraper Sudoku: Perimeter clues showing visible building counts (taller numbers block smaller ones), while unmarked sides remain unrestricted.
Snow Sudoku: No digit repeats in any horizontal row, left diagonal, right diagonal direction, or within each hexagon.
Necklace Sudoku: The numbers in each row, each column, and each necklace (an area formed by multiple connected circles) are all non-repetitive.
Thermo Sudoku: Numbers must strictly increase from the round bulb end to the flat end of each thermometer shape.
Arrow Sudoku: The number in the circle equals the sum of all numbers along its arrow path.
Clone Sudoku: Using colors to mark multiple identically-shaped clone regions, where numbers in corresponding positions across clone regions must match.
Blackout Sudoku: Each row, column, and box must contain unique numbers, but black cells remain empty without digits.
Odd / Even Sudoku: Cells with circles must contain odd digits, cells with squares must contain even digits.
3D Sudoku: Each 3x3 box, as well as the 9 cells along each colored line, contain unique, non-repeating digits.
Samurai Sudoku: Satisfying the classic Sudoku rules in each of the five independent regions.
Inequality Sudoku: Adds symbols such as great than, and the numbers must satisfy the corresponding size relationships.
Fortress Sudoku: Gray fortress cells must contain numbers larger than adjacent white cells.
Kropki Sudoku: Kropki Sudoku: Black dot - ratio of 2; White dot - differ by 1; Others - not satisfy either of these two relationships.
Diagonal Sudoku (X Sudoku): Requiring uniqueness of digits in two major diagonals.