The file size limit in the file system is usually determined by the size of the variable containing its file size. On a file system where the size is defined as a 32-bit unsigned integer, you cannot save a file size larger than 2 ^ 32-1 (= 4294967295). On many modern file systems, the file size is usually saved as 64 bits, which gives a maximum file size of 2 ^ 64 (16 EiB), a very large number.
The maximum size of the file system itself is usually limited by the size of the file system block addresses multiplied by the file system block size. On older FAT16 file systems, addresses were limited to 16 bits (= 65536 unique addresses), and the size of blocks (or clusters) was limited to a maximum of 64 KB, which led to a limitation of the file system size to 4 GB, which was the reason for the larger option , FAT32, has been developed. In modern file systems such as NTFS, ext4, btrfs and many others, the maximum file system size is very large and is unlikely to hit for a long time. However, due to restrictions in the implementations, there are some artificial limitations, which in some cases are lower than the actual format limit, for example, NTFS has a 256 TB file system limit (according to Wikipedia).