Trello also uses a shortId, which is 8 characters. So I created a card and go the key “Qe5yM5cI” which can contain upper and lower case letters and numbers.
Since there are 26 letters in the English alphabet (both upper and lower case) and 10 digits (0-9), there are a total of 26 + 26 + 10 = 62 possible characters that can be used for each position in the key.
To calculate the number of possible permutations of an 8-character key using a 62-character alphabet, we can use the formula for permutations:
n! / (n - r)!
where n is the number of characters in the alphabet (62), and r is the length of the key (8).
Plugging in the values, we get:
62! / (62 - 8)!
= 62 x 61 x 60 x 59 x 58 x 57 x 56 x 55 = 208,304,424,296,960,000
Therefore, there are approximately 208 trillion possible permutations for an 8-character key using a 62-character alphabet. So, 24-character length ID aside, the 8 digit one seems to have a 1 in 208 trillion chance of collision. It would be like winning the lottery 700,000 times in a row – if you could even live that long.