The Kudoku Sudoku solver is probably the fastest Javascript solver to date.
Although faster algorithms exist, they have not been ported to Javascript so far as I know.
(Emerentius's implementation
in web assembly is now several times faster than this page). For more information
on the Sudoku algorithms, see the Wiki page
and my blog post.
To use this solver, you may input multiple puzzles in the textarea or one puzzle in the 9x9 grid, and then click the `Solve' button. Alternatively, you may select text in the textarea to fill the grid or write the puzzle string in URL, for example like this. Example inputs are also provided. Note that solving `Hardest20x50' may take several to tens of seconds with Chrome, FireFox, Safari and Opera. IE6/7/8 may take far longer due to their crappy Javascript engine.
All the HTML and Javascript source codes are distributed under the MIT open-source license.
Samples:| Input or select in the textarea to fill the grid |