A vault is a folder on your Mac that Header treats as a notebook. Each note is a Markdown file in that folder or one of its subfolders, so you can open the same files in Finder, another editor, or a backup tool. Folders you make in Header are real folders on disk.

To add a vault, choose File → Add Vault… (⇧⌘O) and pick a folder. The panel has a New Folder button if you want to start fresh, and you can select several folders at once. If you pick something very broad, such as your home folder, Desktop, Documents, Downloads, iCloud Drive or a whole disk, or a folder that is mostly not notes, Header stops and asks before adopting it. Install, update & first launch walks through that prompt.

You can keep more than one vault, say a Work vault and a Personal one. They all appear under Vaults & Folders in the sidebar, but only one is active at a time. The Library rows, Captures, Pinned and the note list all show the active vault. Its name sits at the top of the sidebar.

Click a vault to open its top level in the note list. Click a folder to list the notes inside it, including those in its subfolders, together with any PDFs, Word files and boards stored there. Clicking a folder in another vault switches to that vault. Switching closes the notes you have open, and Header asks first if any of them has unsaved changes.

Right-click a vault for Use This Vault, Browse All Files, Reveal in Finder, Copy Path, Rename Vault…, New File, New Folder, Refresh Files and Remove Vault. Rename Vault… renames the folder itself on disk. Remove Vault only takes the vault out of Header's sidebar; the folder and its files stay where they are.

Right-click a folder for New Note Here, New Folder Here and Pin to Sidebar. To move a note into a folder, drag it from the note list onto the folder.

Click Explore in the sidebar to open a page of cards. At the top is an Ask your vault box that sends a question to Ask Header, then a Mindprint panel. The cards come in three groups:

Each card has a short status line, for example "Ready · 312 notes indexed", or "Building your index…" while a new vault is first being read. Share Pack says "Needs a Mindprint first" until you have one.

Click the pin on a card to add that tool under Explore in the sidebar. You can pin up to three. Manuscripts, Boards and Research Mode already have sidebar rows, so pinning them doesn't add a second one.

The note list shows whatever the sidebar has selected, with its name and a count at the top. Next to the count are the New Note button (its small menu also has New Canvas) and List Options:

• Sort: Recently Modified, Created, Recently Opened, Starred First, Title or Folder.
• View: Show Previews, Hide Previews, Title Only or Gallery. Gallery shows notes as cards, with its own card size and preview options.
• Only Notes with Images narrows the list to notes that have a picture.

The search field sits under the header. Finding & connecting notes explains it.

The same three layouts are on the Pane Layout control in the toolbar. Text size runs from 11 to 32 points; Actual Editor Text Size puts it back to 15. For a distraction-free view with typewriter scrolling, see Focus Mode in Writing & the editor.

Clicking a note replaces the one in the editor. To keep both, right-click the second note and choose Open in New Tab. A tab strip appears once more than one note is open. Each note gets one tab, so the command is greyed out for a note that already has one.

In the tab strip, click the selected tab's title to rename it, or right-click a tab for Open Tab, Rename, Star Note and Move File to Trash. The + at the end makes a new note, following the same rule as ⌘N.

To give a note its own window, open it and choose Move to New Window from the ⋯ menu in the toolbar. That window has its own tabs: drag them to reorder, and right-click one for Pin Tab, Close Tab, Open in New Window and Reveal in Finder. Locked notes are edited in the main window only.

Right-click a note in the list for these. Several are also in the ⋯ menu at the top right of an open note, under Note.

Before a note goes to the Trash, Header saves a last copy to its history, which you can read about in The Note Inspector & history. To print, share or export a note, see Writing & the editor.

Folders often hold more than Markdown. Header opens other files by type:

• PDF and Word files open in Header's own viewers. Highlighting and pulling quotes into notes are covered in Research & the Reading Room.
• Boards (.canvas files) open in the board editor. See Boards.
• Text and code files, such as .txt, .json, .yaml, .css, .js, .py or .html, open in a plain code editor with Save and Close buttons and an "Unsaved" marker while you have changes.
• HTML files also get a Source / Preview switch. The preview runs with JavaScript turned off and doesn't load anything from the internet.
• Images and videos open in your Mac's default app. Anything else shows a small card with an Open button for the app that owns it and Reveal in Finder.

PDF, Word and board files in a folder have their own right-click menu with Rename File…, Move To and Move to Trash….