Apps similar to GNU GRUB include rEFInd - Boot Manager, which is free and open source. Other options are Limine, Libreboot, Grub2Win and Clover EFI bootloader. You can choose from more than 10 Boot Managers like GNU GRUB for Windows, Linux and Mac.
The Syslinux Project covers lightweight bootloaders for the MS-DOS FAT filesystem (SYSLINUX), network booting (PXELINUX), booting from the ISO 9660 filesystem (ISOLINUX), and Linux ext2/ext3/ext4 or Btrfs filesystems (EXTLINUX).
The development of LILO as classic bootloader for GNU/Linux systems was restarted in June 2010. Because of the simpleness LILO has some advantages comparing with Grub and Grub2. But nowadays LILO is not the bootloader for all situations. But LILO is longtime proved and stable.
United States
Quibble is the custom Windows bootloader - an open-source reimplementation of the files bootmgfw.efi and winload.efi, able to boot versions of Windows from XP to Windows 10 22H2. Unlike the official bootloader, it is extensible, allowing you to boot from other filesystems than...
United Kingdom
rEFIt is a boot menu and maintenance toolkit for EFI-based machines like the Intel Macs. You can use it to boot multiple operating systems easily, including triple-boot setups with Boot Camp. It also provides an easy way to enter and explore the EFI pre-boot environment.
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Chimera is a Hackintosh bootloader that merges the best features from various branches of Chameleon bootloader, into a new branch based on the latest Chameleon 2.0 RC5 trunk version. It is designed for maximum compatibility across platforms.
United States
Written in C++ and licensed under GNU GPL, XOSL (eXtended Operating System Loader) is a user-friendly, window-based graphical boot manager handling large disks and over 30 different operating systems.
Yaboot is a PowerPC bootloader for Open Firmware based machines including New World Apple Macintosh, IBM RS/6000, IBM pSeries and IBM OpenPower machines.
