Make your app work with Thaw

Thaw moves and hides other apps’ menu bar items. Up to macOS 26, each item had a window of its own, so this mostly worked whatever an app did. macOS 27 draws the whole menu bar in one window, and Thaw has to work out which item is which from what each app tells it. What your app does decides whether Thaw can keep its items where people put them.

This page is for the developers of those apps, and came out of a question in Discussions. Most of it was measured while making Barometer work with menu bar managers on macOS 27.

In shortCopy Anchor Link

1. Give every item a fixed autosaveName and accessibility identifier, before it is first shown.
2. Keep changing text, such as a temperature, out of the button’s title. Draw it into the image.
3. Make each item once, and hide it with isVisible.
4. Show each item that should hide on its own from a helper app with its own bundle identifier.
5. Test from /Applications, then check the item in Thaw’s Menu Bar Layout.

How Thaw tells items apartCopy Anchor Link

Thaw knows an item by two things:

1. The bundle identifier of the app that made it.
2. The item’s name, which it reads from the item’s autosaveName and its accessibility title, identifier, description and value.

If either changes, Thaw treats it as an item it has never seen, and the item loses its place. An item that renames itself when its icon changes is a common reason an item seems to wander or go missing.

Give every item a fixed nameCopy Anchor Link

let item = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
// Name it before it is first shown, so it is never seen without one.
item.autosaveName = "com.example.app.cpu"
if let button = item.button {
    button.setAccessibilityIdentifier("com.example.app.cpu")
    button.setAccessibilityLabel("CPU")
}
item.isVisible = true

• Name it before it is shown. Set the autosave name, accessibility identifier and label before the item’s first isVisible. A manager that sees an unnamed item can pair it with the wrong name.
• One name per item, for good. Give each item its own name and never reuse one for different content. A second item of the same kind gets .2, a third .3, and so on.
• Make it once. Keep each item for as long as the app runs, and hide it with isVisible. Removing an item and making it again, or using .removalAllowed, gives a manager a new item each time.
• Leave the window’s title alone. Don’t set the title of the status item’s window.

Keep live values out of the titleCopy Anchor Link

A button title that changes, such as a temperature or a count, becomes the item’s accessibility title, and Thaw reads it as a new name. Draw changing text into the button’s image instead, and give the reading to accessibility as a value:

button.title = ""
button.imagePosition = .imageOnly
button.image = reading // the text, drawn into an image
button.setAccessibilityValue("62 °C")

Apps whose names keep changingCopy Anchor Link

Thaw has worked around a number of apps whose item names change all the time:

• Dato shows the date and a countdown to your next event, so its name keeps changing, whatever date format you pick (#1175).
• Amphetamine’s one item switches between Item-0, ∞ and 𝗧.
• ThermalForge, MacThrottle, Macs Fan Control and iStat Menus show live temperatures and readings.
• Outlook puts a countdown to your next meeting in front of its name.

A fixed name in your own app is the fix that lasts. Each app above needed a change in Thaw itself, and Thaw no longer adds workarounds for single apps.

For these apps, Thaw strips out the changing part of the name, or tells the items apart by where they sit. It learns to do the same for an app with a single item that renames itself, such as WeChat with its unread count.

Position only goes so far. When an app has several items, moving one can swap which is which.

Items with no nameCopy Anchor Link

Set an autosave name and an accessibility identifier, as above, and your items never end up as one of these.

An item that publishes no name of its own gets a placeholder from macOS by its position: Item-0, Item-1 and so on. Thaw can tell two of an app’s unnamed items apart only by their order, so moving one can make them trade places in Layout, or trade sections.

It happened to Rectangle, whose item became Item-0 when its old AppKit placeholder name could no longer be read. Little Snitch had it worst, below.

What Little Snitch went throughCopy Anchor Link

Little Snitch’s agent shows its item through Control Center, so Thaw saw it as com.apple.controlcenter:Item-0, with no name and no app behind it. Thaw had to work out which item was Little Snitch’s by matching it indirectly. For months, people saw what looked like Thaw bugs:

1. It wasn’t listed by name in Layout, and dragging it there didn’t last (#709, #372).
2. It went back to Hidden a few minutes after being moved, and in 2.0.0-beta.13 it wouldn’t stay anywhere (#651, #575, #643).
3. Clicking it while hidden made Thaw’s own icon chase the cursor (#332).
4. Its agent came back twice after the Mac woke from sleep (#641).
5. On macOS 27 it was missing from Thaw altogether, and clicking it opened Thaw’s hidden items, until its GUI Scripting option was turned on (#1179, #1220).

Each one took a fix or a workaround in Thaw, and some still need people to ⌘-drag the icon by hand. An item that comes from your own app’s process, with a fixed name, avoids all of it.

Let each item be hidden on its ownCopy Anchor Link

macOS 27 hides menu bar items by app, not by item. Thaw can tell macOS which apps’ items to hide, so all of one app’s items go to Hidden together, and one item left in Visible keeps the others there too. This is on the roadmap as blocked by macOS 27.

The way round it is to show each item that should hide on its own from a separate app, with its own bundle identifier. Barometer tried this in Barometer#4, with a small helper app inside the main one that shows a single item:

1. Build the helper as an app of its own, with its own bundle identifier, such as com.example.app.gpu. Set LSUIElement to true in its Info.plist, so it has no Dock icon.
2. Put it inside the main app, at Contents/Library/LoginItems/.
3. In the helper, check Bundle.main.bundleIdentifier before you touch NSStatusBar, and make its one item as described above.
4. Sign the helper first, under its own identifier, and then the main app, so the main app’s signature covers a helper that is already signed.
5. Start the helper from the main app, for example with SMAppService.loginItem(identifier:), and make sure only one copy of it runs.

On macOS 27, a menu bar manager then lists the helper’s item on its own, and can hide it while the main app’s items stay visible.

Other things that cost an item its placeCopy Anchor Link

• Don’t edit saved positions. Leave AppKit’s visibility and position defaults, and Control Center’s preferences, alone. An app that wrote to Control Center’s preferences sent its own icon to Hidden in Thaw and other menu bar managers (#605).
• Don’t reorder items from code. Leave where an item sits to macOS and the person using it.
• Let LSUIElement make it an agent. Setting the .accessory activation policy before the run loop starts gives items no height on macOS 27, and no manager can place them.
• Test from /Applications. The same app launched from a build folder can get items with no height. Install it before you judge how it works with a manager.
• Run one copy, and expect to be relaunched. A second launch should hand over to the first one and quit. To apply a new menu bar spacing, Thaw asks apps with menu bar items to quit and opens them again, and an app that also restarts its own helper ends up with two icons.

Check itCopy Anchor Link

1. Open Menu Bar Layout in Thaw’s Settings, and put each of your items in a section.
2. Quit your app and open it again.
3. Check that each item is listed once, under its own name, in the section you put it in.

If it isn’t and you’ve followed this page, open an issue with your app’s bundle identifier and the autosave names of its items.