All the below mentioned Identifiers work fine but people prefer different ones based on their secondary functions. For example, the secondary function of Time IDs is they immediately tell you when the note was created. Some people like having this feature because they think of their notes in a temporal aspect.
Because the UIDs provide different secondary functions, sometimes people like to combine the different ones (e.g. Time ID + Title or Luhmann ID + Title).
- Serial Number - is where you use a counter, increasing it every time you create a note, Note 1, Note 2, Note 3, Note 4, Note 5, Note 6, etc. A zettelkasten program that uses this version would be Zettelkasten^3.
- Luhmann ID - Luhmann used alternating numbers and letters for his zettelkasten (e.g. 3a1p5c4fB1a), this allowed for him to insert a nearly infinite number of notes between any two notes (Johannes F.K. Schmidt 2018, Section 4).
- Time IDs - are timestamps, these are good IDs for a zettelkasten because you can essentially have unlimited ones if you drill down to the minute or second (e.g. 2020070290245). Most people aren’t going to be creating new notes so fast that a minute or second timestamp won’t work.
- Unique Titles - are words, phrases, or sentences that hold semantic meaning and you keep unique to that specific note (.e.g. this note is titled “Note Identifiers”).
Random UIDs - you can have programs that generate seemingly random combinations to stand in as your identifier.
- Random Number - generates a random number, typically using a hash or random number generator.
- Four Letter Words - I see websites (e.g. Twitch - ClumsyWittyDragonBudStar) using random combo of 4 words as the identifier.