Crossword maker
Give it a word and a clue on each line. It works out where the words cross, numbers the grid, and prints with the answers on a separate sheet.
How to write the list
One entry per line, the word first, then the clue: OTTER: river swimmer. A comma or a dash works just as well as a colon. Spaces inside an answer are removed, so ICE AGE becomes one seven-letter entry. A line with no clue still goes into the grid and is listed as having no clue yet, which is useful when you are building the grid first and writing the clues afterwards.
Why a word sometimes doesn't go in
Every entry has to cross an entry that is already placed, sharing a letter at the crossing square. If a word has no letter in common with anything else on the grid, there is nowhere legal to put it and it is reported rather than quietly dropped. Adding one more word that shares a letter with it usually pulls it in. Lists that share plenty of vowels interlock most easily.
The rule that keeps it a crossword
Two entries may only touch at a crossing square. Words never run straight into one another, and a letter that isn't a crossing never sits shoulder-to-shoulder with a neighbour — otherwise the grid would read out words nobody wrote a clue for. That constraint is why the finished grid is a little sparser than you might expect, and why every run of letters in it appears in the Across or Down list.
Printing and the answer key
Press Print or save as PDF. The puzzle and its clues print on the first sheet and the filled grid on a second, so the answers never show through on the handout. Choose Save as PDF in the print dialog if you want a file instead of paper. Nothing is uploaded — the grid is worked out in your browser, so your clues stay on your machine.
Related tools
The word search maker takes the same word list without clues. If you're solving rather than setting, the word finder matches a pattern like C??SS, and the anagram solver handles the anagram clues.