Crossword Grid Builder

I've been getting into crossword constructing, but found the initial process of staring at a blank 15x15 grid to be one of my least favorite parts. Just like themes and seed entries can be good ways to get a foothold, I ended up building this tool to allow you to explore interesting constructions through an interactive heatmap of previous NYTimes puzzles. As you place black squares into the grid it will update the heatmap to only show grids that include those black squares (though ideally you should diverge from history: 70% of published puzzle grids are novel).

Grid UI

This is currently live at It works for all days of the week, along with all NYTimes puzzles from the very first puzzle in 1942 up to today's puzzle (it updates at 8am PDT every day). It has a view of some stats from the grid you're currently building (the number of blocks, the number of words, whether it's valid). For the heatmap, it allows you to choose the days of the week, along with all of the major editors and their eras for specific date ranges.

The editors, and NYTimes in general have changed what patterns they choose over time. Looking at all crosswords between Monday through Saturday there's a pretty consistent grid pattern that holds the same through all of them segmenting around the 5th and 11th rows and columns (though puzzles later in the week have a higher likelihood of breaking that pattern). But if you instead look at the "Modern" era of NYTimes crosswords with Will Shortz, you can see Thursday has taken the spot of Friday/Saturday in terms of the similar pattern with more novelty, while as Friday and Saturday (presumably because of the standardization of them as the spots for themeless with more interesting constructions) tend towards more X patterns and central dividers, with more open grids.

Monday Thursday Friday Saturday
All Cross-words All, Monday All, Thursday All, Friday All, Saturday
Will Shortz Era Will Shortz Era, Monday Will Shortz Era, Thursday Will Shortz Era, Friday Will Shortz Era, Saturday

You can also see this in average number of words. The Will Shortz era has fewer, longer words on Fridays and Saturdays, while also having slightly denser and easier early week grids, presumably to help with themes and approachability.

If you want to see the code behind the tool, it's available on my Github here.