system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can a site like imgur use only six to seven characters in the url for each image uploaded when other sites need to use nearly dozens?

There are millions of images on imgur, but the URLs never have the image code exceed eight characters.  How is that possible when comparing to similar sites that do the same thing as imgur, but have url's so much longer?
gpt
6 characters with the possibilities to have letters and numbers gives a total of 36^6 possibilities, or 2176782336 possibilities. If we use 7 characters it becomes 78364164096 possibilities. If we start using words and numbers, the amount of possibilities is a lot smaller. For example gfycat only uses combinations of words, which becomes very limited and has to add more words or characters to the URL in order to keep up with the amount of posts. 

*imgur also makes a difference between upper and lower case letters, increasing the amount of possibilities to 62^6 (56800235584) or 62^7 ( 3.5216146e+12).