What it is for

A note lives in one folder but is often about several things. Tags cut across folders: tag every note that needs a follow-up, then show just those, wherever they are filed.

How to use it

Create tags in Settings → Tags: type a name and press Enter.
In a note, press the tag icon in the formatting toolbar and click a tag to add or remove it. A dot on the icon means the note has tags.
To filter, press Filter by tags at the top of the sidebar and pick one or more. Only notes with at least one of them are shown, and a number on the icon says how many filters are on.
Click a selected tag again to remove that filter.
Rename or delete tags in Settings → Tags. Deleting a tag removes it from every note.

Examples

Follow-ups across every project

Tag notes follow-up wherever they are filed. On Friday, filter by follow-up and work through the list.

A reading list

Tag articles and book notes reading, so they gather in one view without leaving the topic folders they belong to.

Good to know

Tag names are stored in lowercase and sync to every device.