# Firmware

> Software built into a device to run its hardware, from routers to washing machines.

- Level: Basic
- Topics: Hardware, Software
- URL: https://tidbit.legios.com.ar/firmware/
- In Spanish: [Firmware](https://tidbit.legios.com.ar/es/firmware/)

**Firmware** is the software that lives inside a device and makes its hardware work. It is stored on a memory chip in the device itself, not on a disk you can browse, and it starts running the moment the device gets power. Your router, your TV, your printer, a smartwatch, a car's dashboard and even a computer's keyboard and SSD each have their own firmware.

It sits between the hardware and everything else. In a simple gadget, like a thermostat or a microwave, the firmware is the whole program: it reads the buttons, drives the display and switches the heater on and off. In a computer or a phone, the firmware does the low-level work (waking up the chips, talking to the disk, managing the battery) and then hands over to the operating system. The BIOS and UEFI of a PC are firmware.

The name says where it sits: firmer than software you install, but not fixed forever like the hardware. Manufacturers release **firmware updates** to fix bugs, add features or close security holes, which is why a router or a phone sometimes asks to update and restart. Old devices that no longer get updates are a real risk, because their known vulnerabilities never get fixed. And an update should never be interrupted: if the power goes out halfway, the device can be left unable to start.

## An analogy

The metal drum inside a music box: it comes with the device and decides what it does every time you wind it. Unlike the drum, firmware can be swapped for a newer version with an update.

## Keep in mind

- Stored on a chip inside the device and runs as soon as it powers on.
- Almost every electronic device has it, from routers to keyboards.
- Updates fix bugs and security holes; devices that stop getting them stay exposed.
- Never cut the power in the middle of a firmware update.

## Go deeper

- [Firmware on Wikipedia](https://en.wikipedia.org/wiki/Firmware)
- [Firmware (NIST glossary)](https://csrc.nist.gov/glossary/term/firmware)

## Related terms

- [Chip](https://tidbit.legios.com.ar/semiconductor-chip/): A sliver of silicon carrying billions of tiny switches that compute and remember.
- [Router](https://tidbit.legios.com.ar/router/): The box that connects your devices to each other and to the internet.
- [SSD](https://tidbit.legios.com.ar/ssd/): Storage with no moving parts: where your files live when the power is off.
- [Operating system](https://tidbit.legios.com.ar/operating-system/): The base software that runs a device and lets every app share its hardware.
- [BIOS and UEFI](https://tidbit.legios.com.ar/bios-and-uefi/): The first program a PC runs: it checks the hardware and starts the operating system.
- [Bug](https://tidbit.legios.com.ar/bug/): A mistake in software that makes it behave differently from what was intended.
- [Vulnerability and CVE](https://tidbit.legios.com.ar/vulnerability-and-cve/): A flaw that lets an attacker misuse software, and the public id that names it.