Question

I’m looking for an algorithm – or should I better say: encoding? – to compress integer numbers to short string IDs like URL shorteners use: http://goo.gl/0puu

Url safe base 64 comes close to it, but maybe there is something better.

Requirements:

• as short as possible
• url safe

Answer 1

“yi_H” called base64 “perfect” and after a bit more research I came to the same conclusion, since only the following characters could be used in URLs without worry:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e f g h i j k l m n o p q r s t u v w x y z
0 1 2 3 4 5 6 7 8 9 - _ . ~

Thats 66 characters, whereas base64 only uses 64 characters. The two more possible characters wouldn’t be practical because 66 is not based on 2.

Conclusion: URL safe base64 (offered as part of Apache Commons for example) is perfect for short IDs.