UEFI ONLY MEDIA LEGACY BOOT BIOS when booting from USB flash drive - how to fix the error?

When booting your computer or laptop from a bootable flash drive made with Rufus software, an ERROR message may appear: BIOS / LEGACY BOOT OF UEFI-ONLY MEDIA with an explanation of the error in English and a suggestion to press any key to reboot. .

This manual details what may be causing the error, how to fix the BIOS LEGACY BOOT OF UEFI ONLY MEDIA error and successfully boot from the flash drive.

Cause of BIOS LEGACY BOOT OF UEFI ONLY MEDIA error

Most modern PCs and laptops support two boot modes: UEFI (EFI) and Legacy (CSM, BIOS, Compatibility Support Mode). When writing a bootable flash drive to Rufus, the user selects in which mode it should be written; the default (if nothing is selected) is UEFI mode.

In case you boot from such flash drive in Legacy mode, you will see ERROR: BIOS / LEGACY BOOT OF UEFI-ONLY MEDIA message, and the explanation on the error screen suggests changing the boot mode in BIOS / UEFI settings of your computer, or rewrite the flash drive for another boot mode.

Keep in mind: Even if you have enabled UEFI boot support in your computer's BIOS, Legacy mode may be used by default (if it is also enabled), which will also cause the error in question. One additional point: for Rufus-created boot drives, in addition to the steps outlined below, you may need to disable Secure Boot in BIOS / UEFI.

Boot from a flash drive in UEFI mode

The easiest and fastest solution in our case is to boot from a flash drive in the desired mode. This will work for any computer with UEFI mode support (this boot mode is supported by most newer devices since around 2012).

How to do it? - There are two options:

1. Go into the BIOS of your computer or laptop, and then, normally in the Boot tab (but it can be in other sections like BIOS Features) make sure that the UEFI boot mode is enabled. The item to be changed may be called "UEFI / BIOS Mode", "Boot Mode", or sometimes it is necessary to disable Legacy boot support - set Legacy Support Mode, CSM Support or Compatibility Support to "Disabled". For different BIOS variants the required option may be located in slightly different places and have different names, but it is usually relatively easy to find.
2. Using the Boot Menu at startup - Normally, the key to press to enter the Boot Menu appears at the bottom of the screen when the computer starts up (read more: How to enter the Boot Menu on a computer or laptop). In the boot menu, you can see that the bootable flash drive is displayed twice: once with the UEFI (or EFI) mark and once without it. Select labeling and then the stick will boot without errors.

Creating a Rufus Bootable Flash Drive for BIOS Legacy Mode

If for some reason the above solution is not suitable for you, you can recreate a bootable flash drive in the same Rufus program so that it is ready for Legacy Mode (CSM).

To do this, simply select MBR in "Partition scheme" and "BIOS (or UEFI-CSM)" in "Target system", this item will be selected automatically. After writing the USB drive in this mode, it will not cause ERROR: BIOS / LEGACY BOOT OF UEFI-ONLY MEDIA error when booting with the same boot parameters in BIOS that you used initially.

Video Tutorial

If there are still doubts or something is not entirely clear, ask in the comments, I will try to help.