Question

I am looking for a url encoding method that is most efficient in terms of space. Raw binary (base2) could be represented in base16 which is smaller and is url safe, but base64 is even more efficient. However, the usual base64 encoding isn’t url safe….

So what is the smallest encoding method that is also safe for URLS?

Answer 1

You can use a 62 character representation instead of the usual base 64. This will give you URLs like the youtube ones:
http://www.youtube.com/watch?v=0JD55e5h5JM

You can use the PHP functions provided in this page if you need to map strings to a database numerical ID:

http://bsd-noobz.com/blog/how-to-create-url-shortening-service-using-simple-php

Or this one if you need to directly convert a numerical ID to a short URL string:
http://kevin.vanzonneveld.net/techblog/article/create_short_ids_with_php_like_youtube_or_tinyurl/