What is Zettel ID?
A Zettel ID is a unique identifier assigned to a single note (a “zettel”) in a Zettelkasten-style system so each idea can be referenced and linked reliably. It acts like a permanent address for that note within a personal knowledge network.
Zettel ID (from the German word zettel, meaning ‘slip of paper’) is a convention used in note-taking systems to give each discrete note a unique, stable label. IDs are often timestamp-based (e.g., 202604101430), decimal/hierarchical (e.g., 1a, 1a.1), or randomized (UUIDs). The ID itself carries no required meaning about content — its job is to provide a persistent handle so notes can be cross-referenced, linked, and reordered without ambiguity. In a Zettelkasten approach, Zettel IDs make it possible to build a web of notes where each connection points to an exact, immutable item.
Usage example
You write a short idea about a productivity habit and save it as a new note. Assign it the Zettel ID 202604101030. Later, when writing a longer essay about habit loops, you link to 202604101030 so readers (or your future self) can jump directly to the original idea and see its context and related notes.
Practical application
Zettel IDs matter because they turn loose snippets into a coherent, navigable knowledge base. They prevent duplicate or lost notes, enable precise backlinks and references, and make restructuring or merging ideas safe because links point to identifiers, not fragile filenames or folder paths. For people who capture ideas quickly (including voice-first capture), stable IDs allow automated systems to attach links, build trails of thought, and suggest relevant items for follow-up. Tools like nxt can automatically generate and retain Zettel IDs when capturing spoken notes, making it easier to build a linked archive without manual bookkeeping.
FAQ
Do Zettel IDs have to be human-readable?
No — they only need to be unique. Human-readable timestamp formats are popular because they’re easy to scan and sort, but UUIDs or other schemes work fine if you prioritize collision avoidance or automation.
How should I choose a format for my Zettel IDs?
Pick a format that matches your workflow: timestamps for chronological sorting, decimal for manual hierarchical linking, or UUIDs for fully automated systems. The key rules are uniqueness, immutability (don’t change an ID once assigned), and ease of use for your tools and habits.