---
name: "ykclient"
section: "1"
platform: "linux"
package: "yubico-c-client"
version: "2.15-7"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/ykclient"
---

# ykclient(1)

YubiCloud One-Time-Password Validation Client

## NAME

ykclient - YubiCloud One-Time-Password Validation Client

## SYNOPSIS

**ykclient** \[*OPTION*\]... *CLIENTID YUBIKEYOTP*

## DESCRIPTION

Validate the YUBIKEYOTP one-time-password against the YubiCloud using CLIENTID as the client identifier.

Mandatory arguments to long options are mandatory for short options too.

- **--help**

  Display this help screen

- **--version**

  Display version information

- **--debug**

  Print debugging information

- **--url** URL

  Validation service URL, for example, "https://api.yubico.com/wsapi/2.0/verify"

- **--ca** CADIR

  Path to directory containing Certificate Authoritity, e.g., "/usr/local/etc/CERTS"

- **--cai** CAFILE

  Path to a file holding one or more certificated to verify the peer with

- **--apikey** Key

  API key for HMAC validation of request/response

- **--proxy** ip:port

  Connect to validation service through a proxy, e.g., "socks5h://user:pass@127.0.0.1:1080"

Exit status is 0 on success, 1 if there is a hard failure, 2 if the OTP was replayed, 3 for other soft OTP-related failures.

## REPORTING BUGS

Report bugs at \<https://github.com/Yubico/yubico-c-client\>.