The Animal Crossing letter system, explained

In the world of Animal Crossing, you can indulge in all sorts of delightful activities: living in a village populated entirely by adorable, anthropomorphic animals, crafting cute items out of resources you scavenge, and maintaining friendships with the aforementioned adorable, anthropomorphic animals.

One of the ways to build friendships with the villagers is to send them lovingly-crafted letters. After obtaining stationery from the store, you have the option to compose a message and send it off at the post office to whichever villager you want. And if your letter is good enough, you might just get one in return — with a special present attached.

This, however, has always raised the question: How the heck does the game read your letters?

James Chambers, a security researcher at Red Balloon Security, decided to delve into the mystery behind the letters of Animal Crossing and shared his findings in a Twitter thread.

The minute you drop a letter off at the post office, it is given a score based on seven different checks labeled A through G.

Check A looks out for punctuation and capital letters. Having a punctuation mark at the end of the letter grants 20 points, and every punctuation mark before that must be followed by a capital letter within three spaces, earning or losing 10 points depending.

B checks for common trigrams (three-letter groups) from a table. The total number of trigrams multiplied by three is added to the score.

The next check makes sure that the first character in the letter is capitalized. If it is, that’s 20 points. If not, it costs 10.

D looks for repetition — if a letter is repeated three times in a row, it docks 50 points and stops checking.

E gets a little fancy and checks for the ratio of spaces to non-spaces in the letter. If there’s only spaces or if the ratio of spaces to other characters is less than 20, then the letter loses 20 points. Otherwise, it gains 20.

The next check only occurs if the letter is more than 75 characters long. If it is and has no punctuation for at least 75 more characters, then the score gets a whopping 150-point deduction.

And finally, G checks each group of 32 characters for at least one space. Every time that doesn’t occur, it deducts 20 points.

Essentially, if your letter has decent punctuation and capitalization, and isn’t terribly long, it will receive a good score, because proper grammar is apparently what the villagers of Animal Crossing value in an epistalary companion. A “good” letter has a score of 100 or above, and a “bad” letter has one of 50 or below.

There are, however, ways that you can “hack” this system and turn in a high-scoring letter that is actually total nonsense, as Chambers demonstrated.

Getting special replies with gifts is another rank-system that’s only based on the trigram counts and repeating characters. Up to two points are awarded to the rank, depending on the trigram percentage, and three more if there are no non-space characters repeated more than three times. If there’s a present attached, six points are rewarded. If the total rank is above three, you’ll get a gift in the reply; each level above three comes from a different group of items.

That’s a pretty involved system for virtual letter sending, but we wouldn’t expect any low standards from the picky Animal Crossing villagers.