BOOTX64EFI

BOOTX64.EFI is the canonical filename used by UEFI firmware for a 64-bit boot loader on x86_64 systems. The file is typically stored on the EFI System Partition (ESP), most often at the path EFI/BOOT/BOOTX64.EFI. It serves as a fallback boot loader that the firmware can start when no specific boot option (Boot#### entry) is available in non-volatile memory or when booting from removable media.

The UEFI specification describes boot loaders in the ESP, and BOOTX64.EFI is a widely adopted convention across vendors and operating systems. For 32-bit UEFI systems, a corresponding file named BOOTIA32.EFI is used. In practice, BOOTX64.EFI is often a small stub that loads a more capable bootloader present on the same or another partition, such as GRUB2, Windows Boot Manager (bootmgfw.efi loaded from a separate path), or systemd-boot.

Usage and behavior can vary by firmware implementation. Some firmware may always attempt to load BOOTX64.EFI from the ESP as a last resort if no other boot entries are configured. Copying a bootloader to this location is common for portability, recovery scenarios, or when preparing bootable media intended to work across a range of hardware.

Security considerations include signatures under Secure Boot. A BOOTX64.EFI file may need to be signed with a trusted certificate, or it may be integrated into a chain of trust that validates the subsequent bootloaders it loads.

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