Whereas some applications use file names to uniquely identify notes, Trilium uses the concept of Note ID.

Generally, the Note ID is a 12-character long alphanumeric sequence (including both lower and upper case letter) that is randomly generated for each new note.

## How does the import/export affect the note IDs

When notes are exported, their note ID is kept in the metadata of the export. However when they are imported back in, a new note ID is generated for all the notes. This also includes other entities that are part of the import/export process such as Attachments.

## Note collisions

Since the Note ID is a fixed-width randomly generated number, due to the pigeonhole principle, there is a possibility that a newly created note will have the same ID as an existing note.

Since the note ID is alphanumeric and the length is 12 we have \(62^{12}\) unique IDs. However since we are generating them randomly, we can use a collision calculator such as the one for Nano ID to determine that we'd need to create 1000 notes per hour every hour for 9 centuries in order to have at least 1% probability of a note collision.

As such, Trilium does not take any explicit action against potential note collisions, similar to other software that makes uses of unique hashes such as Git. If one would theoretically occur, what would most likely happen is that the existing note will be replaced by the new one.