Which openings lead to the shortest games? What about the longest games?

For this data I parsed 100 million games from Lichess, from players rated 1200-1800 playing blitz/rapid/classical. There's always a million ways to slice this stuff, but I was mostly curious about the majority of players that fall in the middle of the rating bell curve. Looking at the same stats for master games would be a fun exercise, but then not really applicable to the vast majority of players.

White's first move

I didn't really expect White's first move to have much of an impact on average game length, which is borne out by the data, where pretty much every common first move has an average game length of 32-35 moves. You can't really influence the game length from move 1.

Black's first move

You see about the same range here, from 30 moves on average for the Englund Gambit, to 34 moves on average for the Modern Defense.

The openings that lead to the shortest games

Fast-forwarding a bit, now we're looking across all openings, regardless of depth. Which ones lead to the shortest games? You can see these are some true outliers, the average game length is about 32 moves, but even the longest of these caps out at 21 moves. The criteria for a "miniature" is 25 games, so if you play these openings you'll be playing a lot of miniatures!

The funniest to me is the fool's mate, which I didn't expect to have an actual ECO code, but there it is. Average game length of 2 :D

The next shortest is the Blackburne Shilling Gambit, which is a fun early queen + knight mate:

The most common opening in this list, with nearly 40,000 games played, is the last one, the Italian Game: Two Knights Defense, Traxler Counterattack, Knight Sacrifice Line, which goes like this:

Unlike a lot of the others in this group, this line isn't hugely winning, stockfish gives it +0.8, but it's very sharp. What's sort of funny is that the win-rate is actually in Black's favor. So despite it being winning for White, it's on the list because White often loses quickly after playing into this.

The openings that lead to the longest games

Let's look at the other side – what openings should you play if you want a drawn-out game that lasts as long as possible? These last almost 10 moves more than the average game, or 30% longer. They generally consist of openings that lead to closed positions which will take a while to resolve.

For example, one of these is the Ruy Lopez: Closed, Pilnik Variation, which looks like this:

Closed position, there's no obvious pawn breaks, and it's objectively dead-drawn. Most of the openings in this group have similar characteristics.

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