Have you ever restarted your Mac or reopened an app and noticed that sometimes everything comes back exactly as you left it, while other times you start with a clean slate?

That behavior is controlled by Resume, a feature Apple introduced back in OS X 10.7 Lion. Resume is designed to reopen app windows and documents so you can pick up where you left off after restarting your Mac or relaunching an app. Apple originally introduced it to make macOS behave a little more like iOS, where apps tend to remember your place automatically. In practice, though, the experience was mixed. Some users appreciated jumping right back into their work, while others found it confusing when old documents reopened unexpectedly or windows appeared in different places after changing displays. Apple eventually adjusted the feature so reopening apps and windows became optional.

These days, most of us are used to how iPhones and iPads preserve app state, so the idea of your Mac remembering where you left off may feel more natural. The challenge is that the settings controlling Resume are not always obvious, and it is not immediately clear how they affect your apps.

It helps to know that Resume works in two different situations. One applies when you restart or log out of your Mac and is decided at that moment. The other controls what happens whenever you quit and reopen an app and is managed through a system setting that stays in place until you change it.

The “Reopen Windows” Option at Restart

Whenever you restart, shut down, or log out of your Mac, macOS asks whether you want to reopen your apps and windows when you log back in. You have probably seen the checkbox in the confirmation window labeled “Reopen windows when logging back in.” If that box is selected, macOS will relaunch the apps that were running before the restart and attempt to return you to the same workspace. If you leave it unchecked, your Mac will start up fresh instead, without reopening the apps that were previously in use.

macOS also remembers how you last set that checkbox. If it’s selected when you click Restart, it will be selected the next time as well. The same goes if you leave it unchecked. If you ever force a restart or bypass the confirmation dialog by holding the Option key when choosing Restart or Shut Down, macOS simply uses the last known setting the next time the Mac starts up.

People tend to either love or hate the “Reopen windows” behavior. Some prefer jumping right back into the same workspace after a reboot, while others, including many IT professionals, see a restart as a chance to clear things out and begin fresh. Either approach works. It just depends on how you prefer your Mac to behave.

Controlling Resume When Relaunching Apps

Resume also affects what happens when you quit and reopen individual apps. This behavior is controlled by a setting in System Settings > Desktop & Dock, under the Windows section, labeled “Close windows when quitting an application.”

When the “Close windows when quitting an application” setting is turned on, which is the default, macOS closes all open windows before the app quits. Because those windows are closed first, there is nothing left for Resume to restore the next time you open the app. In practice, that means the app will always launch with a clean slate, unless the app itself has its own way of restoring previous sessions.

If you turn this setting off, macOS behaves differently. When you quit an app, its windows and documents are preserved, and the next time you open the app, Resume will restore them automatically so you can continue where you left off.

Depending on how you prefer to work, Resume can be helpful or occasionally frustrating. There are three common situations where its behavior may stand out, for better or worse:

• Document-centric apps: Apps like Pages or Numbers revolve around individual documents, each opening in its own window. When “Close windows” is enabled, these apps launch fresh each time. When it’s disabled, the documents that were open when you last quit will reopen automatically.
• Unsaved documents: A related situation involves unsaved work. If “Close windows” is on and you try to quit an app with unsaved documents, macOS will prompt you to save before closing the window. If the setting is off, those documents and any unsaved changes will simply reopen the next time you launch the app.
• Window-based apps: Some apps, like Mail or Messages, center around a main window rather than individual documents. They will open that window regardless of the setting. However, Resume still affects where that window appears. When “Close windows” is on, macOS may forget which display or Space the window was using and reopen it on the primary display instead.

Most people don’t realize this “Close windows” setting even exists, let alone what it controls. If you find yourself repeatedly reopening documents in apps like Pages or repositioning windows in apps like Mail every time you relaunch them, it’s worth checking that this setting is turned off. On the other hand, if you prefer apps to open clean each time without restoring previous workspaces, leaving the setting on will give you that fresh start.

Exceptions and Caveats

For most people, the “Reopen windows” checkbox and the “Close windows when quitting an application” setting provide enough control over Resume. However, some users may want more control, or notice that certain apps do not always follow these settings.

• Nonstandard apps: Everything described so far applies to apps built with Apple’s standard development tools. Some apps use their own frameworks or ignore Apple’s conventions. Microsoft apps are a common example, so Word, Excel, or PowerPoint may not follow the Resume settings exactly as expected.
• Turn off Resume for one launch: If you normally allow apps to restore windows by leaving “Close windows when quitting an application” turned off, you can temporarily bypass Resume in some apps by holding the Shift key while launching the app. It does not work everywhere, but it is worth trying.
• Custom session restore: Some apps manage session restoration themselves, including Safari and many Electron-based apps like Slack, Discord, and Notion. For example, Safari lets you choose how it opens under Safari > Settings > General > “Safari opens with.” Options include a new window, a private window, or restoring windows from the previous session. When an app behaves differently from Resume, check its own settings to see how session restoration is handled
• Login Items: Even if you deselect “Reopen windows” when restarting, apps and documents that you’ve added as login items in System Settings > General > Login Items & Extensions > Open at Login will still open. Think of this as a manual Resume—you’ll restart to a preset workspace, not to the way things were when you restarted. Some software may also install helper apps that control what appears at launch.
• Full-screen apps and Spaces: Apps that were last used in full-screen mode reopen into their own Spaces when “Close windows” is disabled. After a restart or relaunch, the app may appear not to have reopened because it is occupying a separate Space that is currently not visible.

In practice, Resume comes down to a simple set of choices:

• If you want your workspace restored after a restart, select “Reopen windows when logging back in.” Ensuring that apps—even if they’re set as login items—open full-screen or in particular Spaces also requires “Close windows when quitting an application” to be turned off.
• If you want apps to remember documents (even unsaved documents), window positions, and displays when you quit and relaunch them, turn off “Close windows.”
• If you want a clean slate, deselect “Reopen windows” and leave “Close windows” turned on.

When windows don’t appear as you expect, check these two settings as your first troubleshooting step.

(Featured image by iStock.com/BigNazik)