ULID vs UUID: Which One Should You Use? 

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From a data block point of view ULID and UUIDv7 are almost the same thing, since they are both 48bit timestamp + "random data". But the 6bit for version and variant of the UUID format makes them incompatible. The conversion from ULID to UUID will result in losing information. Truncating those 6bits and replacing them with v7 and the variant should not be a problem, but in the worst case it may generate collisions. Converting from UUIDv7 to ULID is not a problem since there is no data loss. From a textual representation point of view, the ULID has the advantage to be shorter. Unfortunately there is no standard support for that, but with few lines of code you can also encode the UUID to Base32 and the Base32 to UUID assuming you are interested in converting them (e.g. if you are using type UUID "type" that your language provides). I hope I have answered your question. Thanks for watching!

@@th30z-code yeah I wonder if the difference of 6 bits would make a difference in practical application as of course the length would effect how likely a birthday collision may occur in a distributed system. I am also checking with the spec writer if it would make sense to also standardise on an optional extended ULID that would include a checksum as there may be a chance that people may be writing these IDs down on paper as well. Was looking at Crockford bade32 checksum char which adds 4 more symbols, but his use of = in checksum chars would be hard to use in a url... So might be better if it was appended with a _ to the original ULID string but where the extra characters are the CRC-8 or something easily implemented check instead.

In practices you can ignore the probability to generate a collision with both UUID/ULID. I've seen many systems in production blindly trusting the random implementation (but don't use javascript Math.random(), or any pseudo-random generator for your implementation). But yeah, from a numeric point of view, the missing 6bit makes a difference: with ULID the probability of collision in a given millisecond is 1 out of 1208925819614629174706176 (2^80). with UUIDv7 the probability of collision in a given millisecond is 1 out of 18889465931478580854784 (2^74). but it's still a really really low probability. To me, as for all the error handling logic, the question is: Is my code putting a life at risk or not. if not, you can trust the implementation and don't bother about the collision probability. If your ULID/UUID are generated from an enumerable number of machines, you can switch to a different ID generation strategy and remove completely the problem of collisions and even reducing the length of your IDs. Check out the Twitter Snowflake IDs: ru-vid.comeHr2EIRcYZY

You can use 3rd party libraries that provides already simple functions to generate the uuidv7/ulid. github.com/LiosK/uuidv7 github.com/kripod/uuidv7 github.com/aarondcohen/id128 github.com/ulid/javascript