What is an EFI file?
An .EFI file is an Extensible Firmware Interface File. The UEFI Forum created this format as a modern replacement for the legacy BIOS. This file operates as a boot executable. A computer's motherboard executes these files during the boot process before the operating system loads. They typically contain bootloaders, device drivers, or diagnostic tools.
How to open EFI files?
Computers run .EFI files natively from a UEFI shell during the system startup. You cannot run these files directly within Windows, macOS, or Linux. To inspect the code inside an .EFI file, software developers use reverse-engineering tools like Ghidra or IDA Pro.
You can also use viewer.online/efi. This platform analyzes .EFI files to identify their exact format and creator software, shows which programs can open the file, and usually previews it.
Best practices and troubleshooting
Never execute unknown .EFI files on your computer hardware. Because these files run at the lowest system level, malicious .EFI files can alter your system firmware or bypass security measures. Always test untrusted boot applications inside a virtual machine like QEMU or VirtualBox. If your computer fails to boot and displays an .EFI error, your operating system bootloader is likely missing or corrupt.
Software and tools
Developers compile .EFI files using the EDK II development environment. Standard compilers such as GCC and Microsoft Visual Studio can also generate these executables when properly configured for the UEFI target architecture.
Summary
Because .EFI files use the known EXE format, viewer.online/efi can safely open and display them online, eliminating compatibility problems.