Rufus stops and complains that the image is too big. Before you delete anything or buy a new pen drive, find out which of the two very different size problems you actually have - one has no trick at all, the other fixes itself if you let it.
The ISO image is too big family of errors confuses everyone because two unrelated limits wear the same words. Limit one: the whole ISO is larger than the USB drive - a 6 GB image simply cannot live on a 4 GB stick. Limit two: the drive is big enough, but one file inside the ISO - install.wim - is larger than 4 GB, and the FAT32 file system used for booting cannot hold a file that size. Rufus handles the second one automatically on modern PCs. Mixing the two up is how people waste an hour splitting files they never needed to split.
Compare three numbers. The ISO file size (right-click the ISO, Properties). The drive capacity - and remember an 8 GB pen drive offers about 7.4 GB of real space, because manufacturers count gigabytes differently; that gap is normal, not a fault. And if Rufus or the error mentions a single file, the install.wim size inside the ISO, visible by opening the ISO and looking in the sources folder.
ISO larger than the drive - that is limit one. ISO smaller than the drive but install.wim over 4 GB - that is limit two, and it is the common one with current Windows 11 images.
There is no clever fix here, and any site promising one is wasting your time. A larger image cannot be compressed into a smaller drive by a writing tool. Your real options:
UEFI firmware wants to boot from FAT32, but FAT32 refuses files above 4 GB, and modern Windows images carry a 5 GB-plus install.wim. Rufus resolves the contradiction with its UEFI NTFS bootloader: a tiny FAT32 boot partition starts the machine, then hands over to the NTFS partition holding the big files. On a UEFI PC you do not have to do anything - leave the file system choice on the Windows defaults Rufus suggests, press Start, and the too-large-file problem quietly disappears.
The old manual alternative - splitting install.wim into .swm parts with DISM - still exists, but with Rufus available it is effort without benefit. Reserve it for the rare pure-BIOS machine that cannot use the NTFS handover.
Worth knowing for the comparison: a Ventoy drive never meets limit two at all. Its data partition is exFAT by default, which has no 4 GB file limit, and the ISO is copied as one ordinary file - nothing is extracted, so no single file inside it ever touches a file system limit. If you regularly handle large custom images, that is a genuine Ventoy advantage. But for a standard Windows install from Rufus, do not go splitting or converting anything by hand - the automatic UEFI NTFS route is the fix, and it is already built in.
Both size problems appear in the comparison video, including the moment Rufus switches to its UEFI NTFS arrangement and the write that failed a minute earlier sails through.
Watch Full VideoAlmost certainly not. Drive makers measure a gigabyte as 1,000 MB while Windows measures 1,024 MB, so every drive shows roughly 7 percent less in Windows. A drive showing dramatically less than expected, or shrinking over time, is a different problem - that one can be a fake-capacity stick.
Yes - DISM has a split-image operation that divides install.wim into install.swm parts Setup can still use. It is a valid manual technique, but with Rufus handling the same situation automatically through UEFI NTFS, splitting is only worth it for unusual BIOS-only hardware.
On UEFI systems - effectively all PCs from the last decade - it boots normally, Secure Boot included. Very old BIOS-only machines cannot use the NTFS handover; on those, a FAT32 drive with a split install image is the fallback.