Help & FAQ/Import guides
Notesnook can write your whole account out as a folder of files. Choose the HTML export and nothing is left behind: formatting, notebooks, tags, attachments, and the links between your notes all survive the move.

Notesnook's export dropdown offers Text, Markdown, Markdown + Frontmatter, and HTML. Only HTML keeps everything.
Both Markdown options flatten your notes before writing them: underline, font sizes, and text alignment are gone before the file ever reaches us. The plain Markdown option also writes no tags and no original dates, so every imported note would be untagged and stamped with today's date. We still accept both, and we will tell you what was lost, but HTML is the one to choose.
The Text export has no structure to read and is not accepted.
Your notebooks are rebuilt as real folders, not flattened into tags. A note in Work > Projects lands in a Work > Projects folder, nested up to three levels deep. Notesnook lets you nest notebooks deeper than that, so anything past the third level attaches to the deepest folder and keeps the extra levels as tags. No note loses its place.
Pinned and favorited notes stay marked. Notesnook keeps Pin and Favorite as two separate properties; PrivacyNotes has a single Pinned list, so a note that was either one lands there.
Notesnook supports a few things we do not: custom fonts, font sizes, and text alignment are dropped, and the text they were applied to is kept. Highlighted text becomes bold and the source of any math block is kept as a code block.
Notesnook can also save a backup file ending in .nnbackupz. That is a different thing: it stores every attachment in Notesnook's own encrypted format, which only Notesnook can unpack. Drop one here and we will say so rather than importing half of it. Use "Export all notes" as HTML instead.