Open the TestFlight link on your Mac, install TestFlight from the App Store if you don't have it, then install HeaderNotes. This build runs in Apple's App Sandbox, so it leaves out a few things that need to run other programs or look around your disk. Pick one version and stick with it.

The two versions keep separate settings. Your notes are files in your vault folder, so switching versions only means choosing that folder again.

Header reads every note in your vault to build search, links and Today, so pointing it at your whole Documents folder makes it slow, and every stray Markdown file there shows up as a note. Before adopting a folder, Header takes a quick count and stops to ask if:

• the folder is your home folder, Desktop, Documents, Downloads, Library, Pictures, Music, Movies, the top of iCloud Drive, or the top of a disk;
• it holds more than 5,000 files or 500 folders and most of them aren't notes;
• or Header can't finish counting within two seconds, which usually means a network drive or iCloud files that aren't downloaded.

The sheet tells you what it counted (“It has more than 5,000 files, and at least 37 of them are notes.”) and offers:

• Create “Header Notes” Inside It, the recommended choice. Header makes a Header Notes folder inside the one you picked and uses that. If the folder already exists, the button reads Use “Header Notes” Inside It.
• Choose Another Folder… reopens the folder picker.
• Use “Documents” Anyway (with your folder's name) opens it as is. The first scan can take a while, and files iCloud hasn't downloaded are left alone.
• Cancel adds nothing.

The same check runs for every folder you add: at first launch, from File → Add Vault…, from a suggested folder, and when you open a folder as a vault from Bring Notes into Header.

If you used the download version first, the TestFlight version can copy across your vault list and settings. Look for Used Header before this version? on the vault screen at first launch and click Bring Over…, or use Settings → General → Vault → Earlier Header setup → Bring Over… later.

1. Header asks you to open the earlier version's settings file. It only reads it; the download version isn't changed.
2. A review sheet lists the earlier vaults and the settings it will bring over. Settings you've already changed in TestFlight stay as they are unless you tick Use the earlier values for these too. Window positions, caches and settings this version doesn't use are left behind.
3. Tick Also copy speaker voice profiles and Atlas pages if you want those too. It asks for access to one more folder and never replaces files already in this version.
4. Click Bring Over. macOS asks you to allow access to each vault folder once, because this version runs in the App Sandbox. If settings came across, quit and reopen Header to apply them all.

Download version. Header checks headernotes.com once a day for a newer beta. The check doesn't send anything from your notes. When an update is ready, Header tells you, and it downloads and installs only after you click. You can check at any time with Header → Check for Updates…, and turn the daily check off with Settings → General → Updates → Check for updates automatically.

TestFlight version. Header doesn't check for updates itself, and the Updates setting isn't shown. TestFlight takes care of new builds.

To see what changed in the build you're running, choose Help → What's New.

Turn on Launch Header at login to have Header start when you sign in to your Mac. Launching at login never turns on the microphone.