---
name: "u2f"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/u2f"
---

# u2f(4)

FIDO/U2F USB security keys

## NAME

**u2f** – FIDO/U2F USB security keys

## SYNOPSIS

**device u2f**

In [loader.conf(5)](/loader.conf/5.md): **u2f\_load="YES"**

In [sysctl.conf(5)](/sysctl.conf/5.md): **hw.hid.u2f.debug**

## DESCRIPTION

The **u2f** driver provides support for FIDO/U2F-compatible USB security keys. They are Human Interface Devices (HID) which can be accessed via the */dev/u2f/N* interface.

The driver is compatible with the [read(2)](/read/2.md), [write(2)](/write/2.md), and [ioctl(2)](/ioctl/2.md) operations of the generic [uhid(4)](/uhid/4.md) device but only accepts the optional HID [ioctl(2)](/ioctl/2.md) calls from u2f group users.

## HARDWARE

The **u2f** driver supports FIDO/U2F-compatible USB security keys.

## SYSCTL VARIABLES

The following variables are available as both [sysctl(8)](/sysctl/8.md) variables and [loader(8)](/loader/8.md) tunables:

- *hw.hid.u2f.debug*

  Debug output level, where 0 is debugging disabled and larger values increase debug message verbosity. Default is 0.

## FILES

- */dev/u2f/\**

  ## SEE ALSO

[uhid(4)](/uhid/4.md), [usb(4)](/usb/4.md), [usbhid(4)](/usbhid/4.md)

## HISTORY

The **u2f** driver first appeared in FreeBSD 15.0.

## AUTHORS

The **u2f** driver was written by Vladimir Kondratyev ⟨*wulf@FreeBSD.org*⟩.

This manual page was written by Vladimir Kondratyev ⟨*wulf@FreeBSD.org*⟩ based on the OpenBSD [fido(4)](/fido/4.md) manual page.