| extension | Valid platforms | Description | 
|---|---|---|
| .pxe | pcbios | Headerless X86 assembly code, PXE- or NBP-booted, sometimes renamed to .0 to work on older DHCP/TFTP servers | 
| .efi | efi | EFI executable | 
| .kpxe | pcbios | Same as .pxe but will Keep the original UNDI stack/driver present. This is needed for undionly ref | 
| .kkpxe | pcbios | Same as .kpxe but will not unload (Keep) the PXE base code. only use with buggy BIOSes | 
| .lkrn | pcbios | Builds with kernel header similar to Linux so it can be started by many bootloaders | 
| .iso | pcbios | Builds .lkrn and adds ISOLINUX to create CD-ROM image, can be started by many bootloaders | 
| .hd | pcbios | Direct executable i386 code put on a harddisk image (32KB blocks) | 
| .dsk | pcbios | Direct executable i386 code put on a floppy disk image (512 Byte blocks) | 
| .pdsk | pcbios | Padded .dsk to work with loaders that requires exact size such as iLO | 
| .usb | pcbios, efi | Same as .dsk for pcbios, in efi mode it's an 1440K image with partition and [driver].efi added as /efi/boot/boot[arch].efi, mostly used for making USB stick images | 
| .rom | pcbios | File intended to be flashed into PCI-based NIC ROM | 
| .mrom | pcbios | File intended to be flashed into PCI-based NIC ROM. See notes for .mrom | 
| .pcirom | pcbios | Same as .rom | 
| .isarom | pcbios | File intended to be flashed into ISA-based NIC ROM, must be used with e.g. VirtualBox | 
| .efidrv | efi | Driver for NIC which can be used by other EFI firmware | 
| .efirom | efi | File intended to be flashed into NIC ROM for EFI | 
| .linux | linux | Linux ELF executable, use for tests and tap drivers |