Provides library functionality for communicating with a FIDO device over USB as well as verifying attestation and assertion signatures.

This library aims to support the FIDO U2F and FIDO 2 protocols for communicating with a USB authenticator via the Client-to-Authenticator Protocol (CTAP 1 and 2). In addition to this low-level device access, classes defined in the fido2.client and fido2.server modules implement higher level operations which are useful when interfacing with an Authenticator, or when implementing WebAuthn support for a Relying Party.

For usage, see the examples/ directory.


These links related to WebAuthn and FIDO2 can help you get started:


This project, with the exception of the files mentioned below, is licensed under the BSD 2-clause license. See the COPYING file for the full license text.

This project contains source code from pyu2f ( which is licensed under the Apache License, version 2.0. These files are located in fido2/hid/. See, or the COPYING.APLv2 file for the full license text.

This project also bundles the public suffix list ( which is licensed under the Mozilla Public License, version 2.0. This file is stored as fido2/public_suffix_list.dat. See, or the COPYING.MPLv2 file for the full license text.


fido2 is compatible with Python 3.7 and later, and is tested on Windows, MacOS, and Linux. Support for OpenBSD, FreeBSD, and NetBSD is provided as-is and relies on community contributions.


fido2 is installable by running the following command:

pip install fido2

To install the dependencies required for communication with NFC authenticators, instead use:

pip install fido2[pcsc]

Under Windows 10 (1903 or later) access to FIDO devices is restricted and requires running as Administrator. This library can still be used when running as non-administrator, via the fido.client.WindowsClient class. An example of this is included in the file examples/

Under Linux you will need to add a Udev rule to be able to access the FIDO device, or run as root. For example, the Udev rule may contain the following:

#Udev rule for allowing HID access to Yubico devices for FIDO support.

KERNEL=="hidraw*", SUBSYSTEM=="hidraw", \
  MODE="0664", GROUP="plugdev", ATTRS{idVendor}=="1050"

There may be a package already available for your distribution that does this for you, see:

Under FreeBSD you will either need to run as root or add rules for your device to /etc/devd.conf, which can be automated by installing security/u2f-devd:

pkg install u2f-devd


This project depends on Cryptography. For instructions on installing this dependency, see

NFC support is optionally available via PC/SC, using the pyscard library. For instructions on installing this dependency, see


For development of the library we use poetry. To set up the dev environment, run this command in the root directory of the repository:

poetry install

We also use pre-commit to run some scans on the code prior to committing.

Running tests

While many tests can run on their own, some require a connected U2F or FIDO2 device to run.

poetry run pytest