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, skyscrapers sudoku, thermo sudoku, arrow sudoku, clone sudoku, odd/even sudoku, palindrome sudoku, sandwich sudoku, little killer sudoku, inequality sudoku, fortress sudoku, v-shaped sudoku, tripod sudoku, between sudoku, German whispers sudoku, slanted-lines sudoku, odd-even capsules sudoku, kropki sudoku, outside sudoku, battenburg sudoku, consecutive sudoku, quad max sudoku, clock face sudoku, clock sudoku, quadruple sudoku, exclusion sudoku, star product sudoku, next to 9 sudoku, Rossini sudoku, x-sums sudoku, search 6 sudoku, search 9 sudoku, odd-even minesweeper sudoku, wheels sudoku, rhombus sudoku, odd-even lines sudoku, anti-diagonal sudoku, triangle sums sudoku, slanted # sudoku, eliminate sudoku, slow thermo sudoku, renban sudoku, diagonal inequality sudoku, parity lines sudoku, point to next sudoku, odd path sudoku, trench sudoku, diagonal consecutive sudoku, OEBS sudoku, descriptive pairs sudoku, numbered rooms sudoku, first odd/even sudoku, rougamo sudoku, sum max min sudoku, distance sudoku, even sandwich sudoku, next to 6 sudoku, bouncing x-sums sudoku, x-th sum sudoku, consecutive count sudoku, max-position sudoku, pointing evens sudoku, diagonal outside sudoku, big-small sudoku, VX sudoku, 56 sudoku, irregular dots sudoku, consecutive pairs sudoku, add/sub sudoku, self joint sudoku, necklace sudoku, blackout sudoku, one more num sudoku, snow sudoku, hexagonal sudoku, curve sudoku, tridoku, hoshi sudoku, 4x4 ring sudoku, half sudoku, honeycomb sudoku, 3D sudoku, cube sudoku, pentagram sudoku, penrose triangle sudoku, 3D windmill sudoku, overlapping sudoku, samurai sudoku, twodoku, triple doku, flower sudoku, windmill sudoku, gattai-3 sudoku, butterfly sudoku, cross sudoku, sohei sudoku, W sudoku, gattai-5 sudoku, gattai-13 sudoku, star sudoku, extra regions sudoku, diagonal sudoku, windoku, offset sudoku, percent sudoku, asterisk sudoku, girandola sudoku, center dot sudoku, pyramid sudoku, product sudoku, ratio sudoku, addition sudoku, subtract sudoku, round off sudoku, sum or difference sudoku, mathdoku, zero sudoku, prime sudoku, sum dot sudoku, inclusion sudoku, diagonal XV pairs sudoku, sum-product VX sudoku, greater sudoku, quad-exist sudoku, consec-ineq sudoku, BMS sudoku, sum frame sudoku, big-small sudoku, odd sudoku, even sudoku, balanced sudoku, non-consecutive sudoku, no touch sudoku, anti-knight sudoku, anti-bishop sudoku, no-four sudoku, connected irregular sudoku, scattered sudoku, shape 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: 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.
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.