Generating Random Unique IDs
Aug 6, 2021
2 minute read

While looking at the Aftership API, I noticed their public tracking IDs looked interesting. Example h4qys6mtkkhnkkjvco35a017 This led me down a path of trying to understand what those values could be and how to make them on my own.



  • Base16
  • Base32
    • alphanumeric, single case
  • Base58
    • alphanumeric
    • excludes letters which might look ambiguous when printed (0 - zero, I - capital i, O - capital o and l - lower case L).
  • Base62
    • alphanumeric, excludes +/ from the alphabet
  • Base64
    • Certain characters, notably “+” and “/” in the base 64 alphabet, are treated as word-breaks by legacy text search/index tools.

See RFC4648 for Base16, Base32 and Base64 specs.


A few versions. 4 is the most recent, which is completely random.

  • 128 bits
  • UUIDv4 are not sortable by time


  • Sortable by time


Distributed Key Generation

MongoDB ObjectID

  • 4-byte timestamp value, representing the ObjectId’s creation, measured in seconds since the Unix epoch
  • 5-byte random value
  • 3-byte incrementing counter, initialized to a random value