Firmware is permanent software programmed into hardware devices that provides low-level control for the device's specific functions. It sits between hardware and software—more permanent than regular software but more changeable than physical hardware. Examples include your computer's BIOS, the software in your router, the controller in your SSD, and the programming in devices like printers, keyboards, and smart home gadgets.
Why it matters
Firmware makes hardware useful by telling it how to operate. The lesson Device Drivers explains how the operating system communicates with hardware, but firmware is even lower-level—it's the intelligence embedded in the hardware itself. When you update your router's firmware or your SSD's firmware, you're improving how that hardware operates at its most fundamental level.
How firmware differs from software
Regular software runs on top of an operating system and can be easily installed, updated, or removed. Firmware is embedded in the device itself, stored in ROM or flash memory on the hardware. It runs without an operating system—in fact, your computer's firmware (BIOS) runs before the operating system even loads, as described in What Happens During Startup?.
Firmware updates
Manufacturers release firmware updates to fix bugs, improve performance, patch security vulnerabilities, or add features. Updating firmware is typically more involved than updating software—a failed firmware update can sometimes make a device unusable ("bricking" it). Modern devices often update firmware automatically or through dedicated update tools.