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The installer USB won't show up

You built the installer, you're holding Option, and the boot picker shows only your internal drive. In most cases the USB is fine and one specific step was missed — and there's one cause that accounts for more of these than all the others combined.

Applies to: Creating a macOS installer with OCLP · all supported models

The short answer

You most likely created the installer but never wrote OpenCore to it. In OCLP, Create macOS Installer and Build and Install OpenCore are two separate operations, and an unsupported Mac cannot boot the installer without the second one.

Run Build and Install OpenCore, target the USB, then look for the EFI Boot entry in the picker rather than the macOS installer entry.

Check these in order

1

Did you install OpenCore onto the USB?

This is the answer far more often than anything else. Creating the installer only copies Apple's installer. Your Mac is unsupported, so it needs OpenCore on the USB's EFI partition before it will boot it. OCLP → Build and Install OpenCore → select the USB.

2

Are you looking for the right entry?

Once OpenCore is on the stick, the entry you want is labelled EFI Boot, often with a plain drive icon. Selecting the “Install macOS…” entry directly bypasses OpenCore and fails.

3

Try a USB 2.0 port, directly.

Older Macs are unreliable booting from USB 3 ports, and worse through hubs, keyboards or dongles. Use a port on the Mac itself, and on models that have both, prefer the USB 2.0 one.

4

Verify the partition scheme.

Disk Utility → View → Show All Devices, select the physical USB device (the top-level entry, not the volume) and erase as Mac OS Extended (Journaled) with GUID Partition Map. MBR-formatted sticks won't appear, and getting this wrong is easy because Disk Utility hides the device by default.

5

Try a different stick.

Cheap and failing flash drives are common, and a marginal one will write the installer without error yet fail to boot. If everything above is right, suspect the hardware — ideally use a known-good 16 GB or larger drive.

Making one correctly, start to finish

For reference, the full sequence — both halves, in order:

  1. Open OCLP and choose Create macOS Installer.
  2. Pick the macOS version. OCLP downloads it (several gigabytes — this is the slow part) and writes it to the USB.
  3. Back at the main menu, choose Build and Install OpenCore.
  4. Target the USB drive, not the internal disk.
  5. Reboot holding Option, and choose EFI Boot.
Before you start

Check the macOS version you're about to install against the supported Macs list first. Nothing is more deflating than a two-hour download and install for a version your Mac was never going to run well.

Other things that produce this symptom

  • A firmware password. It blocks alternate boot devices outright — the picker either won't appear or won't offer the USB. It must be removed first, and on these older Macs that means Apple support with proof of purchase.
  • A failing USB port. Try the same stick in every port before blaming the stick.
  • An interrupted download. If OCLP's installer download was cut off, the USB can look complete but hold an unbootable installer. Recreate it rather than trying to repair it.
  • Wireless keyboard timing. On desktops, a Bluetooth keyboard often isn't awake early enough for Option to register. Use a wired keyboard for this.

Common questions

How big does the USB drive need to be?

16 GB is the practical minimum for recent macOS versions and 32 GB gives you room to spare. The installer alone is around 12–15 GB for current releases.

Can I use an external SSD instead of a flash drive?

Yes, and it's substantially faster and more reliable. The same rules apply: GUID Partition Map, and OpenCore installed to it.

Do I still need the USB after macOS is installed?

Not for daily use, but keep it. It's the recovery route when the internal OpenCore breaks — see Mac stuck on boot.

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