netboot.xyz is described as 'Way to select various operating system installers or utilities from one place within the BIOS without the need of having to go retrieve the media to run the tool' and is a bootable usb creator in the cd/dvd tools category. There are three alternatives to netboot.xyz for Windows and Linux. The best netboot.xyz alternative is Ventoy, which is both free and Open Source. Other great apps like netboot.xyz are MultiBootUSB and TekDT USB Creator.
Ventoy is an open source tool to create bootable USB drive for ISO files. With ventoy, you don't need to format the disk again and again, you just need to copy the iso file to the USB drive and boot it.
MultiBootUSB is a software to create multi boot live Linux on a removable media i.e USB disk. It is similar to UNetbootin but many distros can be installed, provided you have enough space on the disk.
TekDT USB Creator is an automatic Windows installation USB/Hard drive creation free software. Help you install Windows for your computer as quickly, simply and as easily as possible.
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Ventoy is to boot from images stored in physical USB drives, while netboot.xyz is to boot from network (PXE).