URL safe UUIDs in the smallest number of characters

Question

Ideally I would want something like example.com/resources/äFg4вNгё5, minimum number of visible characters, never mind that they have to be percent encoded before transmitting them over HTTP.

Can you tell a scheme which encodes 128b UUIDs into the least number of visible characters efficiently, without the results having characters which break URLs?

Answer 1

Base-64 is good for this.

{098ef7bc-a96c-43a9-927a-912fc7471ba2}

could be encoded as

vPeOCWypqUOSepEvx0cbog

The usual equal-signs at the end could be dropped, as they always make the string-length a multiple of 4. And instead of + and /, you could use some safe characters. You can pick two from: - . _ ~

More information:

• RFC 4648
• Storing UUID as base64 String (Java)
• guid to base64, for URL (C#)
• Short GUID (C#)

Answer 2

I use a url-safe base64 string. The following is some Python code that does this^*.

The last line removes '=' or '==' sign that base 64 encoding likes to put on the end, they make putting the characters into a URL more difficult and are only necessary for de-encoding the information, which does not need to be done here.

import base64
import uuid

# get a UUID - URL safe, Base64
def get_a_Uuid():
    r_uuid = base64.urlsafe_b64encode(uuid.uuid4().bytes)
    return r_uuid.replace('=', '')

Above does not work for Python3. This is what I'm doing instead:

 r_uuid = base64.urlsafe_b64encode(uuid.uuid4().bytes).decode("utf-8")
 return r_uuid.replace('=', '')

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^* _{This does follow the standards: base64.urlsafe_b64encode follows RFC 3548 and 4648 see https://docs.python.org/2/library/base64.html. Stripping == from base64 encoded data with known length is allowed see RFC 4648 §3.2. UUID/GUID are specified in RFC 4122; §4.1 Format states "The UUID format is 16 octets". The base64-fucntion encodes these 16 octets.}