---
id: fido2
version: "2.2.1"
license: Copyright (c) 2018 Yubico AB All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: *… (full text in the JSON record)
license_treatment: unclear
maintenance: active
---

# fido2 — FIDO2/WebAuthn library for implementing clients and servers.

License: unclear · Maintenance: active · Downloads: 2.6M/mo

## What it is and what it does

fido2 is a Python library for implementing FIDO2 and WebAuthn authentication flows. It provides low-level device communication with USB authenticators via the CTAP 1 and 2 protocols, as well as higher-level client and server classes for building passwordless authentication systems. The library handles cryptographic verification of attestation and assertion signatures, making it suitable for both authenticator clients and relying party (server) implementations.

The package depends only on cryptography and is actively maintained by Yubico. It supports Windows, macOS, and Linux, though platform-specific setup is required—particularly on Linux where Udev rules must be configured for HID device access. Optional NFC support is available via the pyscard library when installed with the [pcsc] extra.

Use it for:

- Build a WebAuthn-compliant authentication server that accepts FIDO2 devices like YubiKeys for passwordless login.
- Implement a desktop or CLI application that communicates directly with USB authenticators for cryptographic operations.
- Verify FIDO2 attestation signatures to ensure authenticators are genuine during registration flows.
- Add second-factor authentication support to an existing application using standard FIDO2 devices.
- Develop cross-platform security tools that interact with hardware security keys.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Implements FIDO2 and WebAuthn protocols for communicating with USB authenticators and verifying cryptographic signatures for passwordless authentication.

Yes. Active maintenance, low install friction, no known vulnerabilities, and production-stable status make this suitable for production use. The multi-license composition requires license review, but is clearly disclosed. Install if you need FIDO2/WebAuthn support; the platform-specific setup (especially Linux Udev rules) is a one-time operational concern, not a blocker.

## Install

pip install fido2
uv add fido2
poetry add fido2

## Installing fido2

Before you install: Low install friction with a single runtime dependency (cryptography). Active maintenance with a recent release 46 days ago and ongoing repository activity. Requires Python 3.10 or later.

License in practice: Multi-licensed: primarily BSD 2-clause, with Apache 2.0 code in fido2/hid/ and Mozilla Public License 2.0 for bundled public suffix list. Verify compatibility with your project's license policy before use.

Quickstart:

pip install fido2

from fido2.client import ClientData
from fido2.server import Fido2Server

server = Fido2Server(rp_id='example.com')

Requires Python 3.10 or later. On Windows 10+, USB device access requires Administrator privileges or use of WindowsClient. On Linux, requires Udev rules or root access for HID device communication.

Verify before relying:

- Whether the library supports the latest FIDO2 specification versions beyond what the description states.
- Performance characteristics when handling multiple concurrent authenticator connections.
- Specific error handling and recovery behavior for device disconnection or communication failures.

## Package facts

- License: Copyright (c) 2018 Yubico AB All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: *… (full text in the JSON record) (unclear)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 2.6M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

fido2 webauthn library, u2f authenticator client, ctap protocol implementation, passwordless authentication, yubikey fido2 support, webauthn server implementation, fido device communication, authentication, cryptography, hardware-security-keys

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