Why does Fedora use FAT32, ext4, and Btrfs for different boot partitions?

The EFI System Partition has to use FAT32 because UEFI firmware is designed to read it. It contains bootloader files that the motherboard can access before Linux starts. FAT32 is limited, but it only needs to hold a small amount of boot data, so that limitation usually doesn’t matter.

ext4 is commonly used for /boot because it is mature, simple, reliable, and widely supported by bootloaders such as GRUB. The /boot directory contains kernels and initramfs files. Btrfs can be read by modern GRUB versions, but keeping /boot on ext4 can still provide a straightforward and compatible setup, especially with encryption or unusual storage configurations.

Btrfs is used for the main system because it supports features ext4 does not, including copy-on-write, snapshots, subvolumes, checksums, and convenient rollback workflows. Snapshots can be useful before upgrades, although they are not automatically a complete backup. ext4 is a good general-purpose choice when you want simplicity and stability, XFS is often selected for large filesystems and workloads, and ZFS offers extensive storage-management features but has additional licensing and kernel-integration considerations. There is no single best filesystem; the choice depends on the features and workload you need.