URL-Compact representation of GUID/UUID?

Question

I need to generate a GUID and save it via a string representation. The string representation should be as short as possible as it will be used as part of an already-long URL string.

Right now, instead of using the normal abcd-efgh-... representation, I use the raw bytes generated and base64-encode them instead, which results in a somewhat shorter string.

But is it possible to make it even shorter?

I'm OK with losing some degree of uniqueness and keeping a counter, but scanning all existing keys is not an option. Suggestions?

Answer 1

I used an Ascii85 encoding for writing a Guid to a database column in 20 ASCII characters. I've posted the C# code in case it is useful. The specific character set may be different for a URL encoding, but you can pick whichever characters suit your application. It's available here: What is the most efficient way to encode an arbitrary GUID into readable ASCII (33-127)?

Answer 2

Sure, just use a base larger than 64. You'll have to encode them using a custom alphabet, but you should be able to find a few more "url-safe" printable ASCII characters.

Base64 encodes 6 bits using 8, so a 16 byte GUID value becomes 22 bytes encoded. You may be able to reduce that by a character or two, but not much more.