There are plenty of good reasons for starting up, or restarting, in Recovery Mode. But which Recovery Mode should you choose? This article provides you with a structured series of decisions which should ensure that you don’t make the wrong choice, and end up wasting time and effort as a result.

You wish to install or re-install macOS

Assuming that your Mac has at some time run Sierra 10.12.4 or later, you need to decide first:

1. Have you made a recent backup from which you can restore your apps and documents, etc.? If you haven’t, now is the time to make one before entering Recovery Mode.
2. Do you want to make a clean (re)install, in which you format your storage before installing macOS? Guidance on this is available here. If you do, then a very recent backup or two is essential, and you should check that those backups will restore properly.
3. Which version of macOS do you want to (re)install?

Recovery Mode gives you three options as to the version of macOS which will be (re)installed, depending on which keys you hold to enter the mode:

• to (re)install the most recent version of macOS which you already have installed, hold Command-R;
• to install the latest version of macOS which is compatible with that Mac, hold Option-Command-R;
• to install the closest version available to that which shipped on your Mac, hold Shift-Option-Command-R.

For Macs which are still running macOS prior to 10.12.4, see below.

When your Mac starts up in Recovery Mode, if you want to perform a clean install onto freshly formatted storage:

1. select Disk Utility,
2. format the correct startup disk,
3. run Reinstall macOS.

If you don’t want to format your storage, proceed straight to Reinstall macOS.

You don’t want to (re)install macOS

If you want access to other tools and features which are provided in Recovery Mode, such as the command line to change SIP configuration, or the Startup Security Utility to change T2 Secure Boot settings, or Disk Utility, then:

• If your Recovery Volume is functioning normally, hold Command-R to enter local Recovery Mode, which is by far the quickest.
• If your Recovery Volume is damaged or dysfunctional, hold Option-Command-R to enter remote Recovery Mode, which will be slower.

If you only want access to command tools available in Recovery Mode, you may be able to go straight into Terminal by holding Command-R-S, but this currently doesn’t appear to be documented by Apple.

If you need access to command tools on your normal boot volume from Recovery Mode:

1. hold Command-R to enter local Recovery Mode,
2. open Disk Utility,
3. select your normal startup volume,
4. use the Mount command in the File menu to mount it,
5. switch to Terminal,
6. enter commands at the prompt, remembering to use the correct path to any on your normal startup volume.

You want hardware diagnostics

You’ve come to the wrong place: hold the D key during startup, and read this article for full details.

Macs running macOS before 10.12.4

Macs which have never had Sierra 10.12.4 or later installed have a different set of installation options:

• to (re)install the most recent version of macOS which you already have installed, hold down Command-R;
• to install the closest version available to that which shipped on your Mac, hold down Option-Command-R.

Multiple startup disks

If your Mac can start up from more than one startup disk, for example if you have a bootable external drive connected, then when you (re)start in Recovery Mode, the Recovery Volume used will be that corresponding to the currently-set Startup Disk. This is particularly important when there are different versions of macOS available on startup disks: if you want to start up in a specific (or different) Recovery Mode, then ensure that you select the appropriate one in the Startup Disk pane before restarting in Recovery Mode.

Thanks to Jeff Johnson @lapcatsoftware for pointing this out.