---
title: "Start login with an existing passkey (Conditional UI)"
method: POST
path: "/passkey/mediation/start"
tags: ["Passkeys"]
---

# Start login with an existing passkey (Conditional UI)

`POST /passkey/mediation/start`

Starts login with an existing passkey in [Conditional UI](https://www.corbado.com/glossary/conditional-ui) scenario. To complete the ceremony you need to call [finish](/api-reference/backend-api/passkeys/finish-login-with-an-existing-passkey-conditional-ui).

## Request body

- PasskeyMediationStartReq
  - `clientInformation` ClientInformation, required
    - `remoteAddress` string, required — Client's IP address
    - `userAgent` string, required — Client's user agent
    - `clientEnvHandle` string — Client's environment handle
    - `javascriptFingerprint` string — Client's fingerprint
    - `javaScriptHighEntropy` JavaScriptHighEntropy
      - `platform` string, required
      - `platformVersion` string, required
      - `mobile` boolean, required
    - `bluetoothAvailable` boolean — Client's Bluetooth availability
    - `passwordManagerAvailable` boolean — Client's password manager availability
    - `userVerifyingPlatformAuthenticatorAvailable` boolean, required
    - `conditionalMediationAvailable` boolean, required
    - `clientCapabilities` ClientCapabilities, required
      - `conditionalCreate` boolean
      - `conditionalMediation` boolean
      - `hybridTransport` boolean
      - `passkeyPlatformAuthenticator` boolean
      - `userVerifyingPlatformAuthenticator` boolean
    - `privateMode` boolean
    - `parsedDeviceInfo` ParsedDeviceInfo, required
      - `browserName` string, required
      - `browserVersion` string, required
      - `osName` string, required
      - `osVersion` string, required
    - `nativeMeta` NativeMeta
      - `build` string, required
      - `deviceOwnerAuth` string
      - `isPlatformAuthenticatorAPISupported` boolean
      - `isBluetoothAvailable` boolean
      - `isBluetoothOn` boolean
      - `googlePlayServices` boolean
      - `deviceSecure` boolean
      - `brand` string
      - `model` string
  - `processID` string

## Response `200`

Passkey login process has been started.

- PasskeyMediationStartRsp
  - `loginAllow` boolean, required
  - `assertionOptions` string, required

## Other responses

- `default` — Error

---

[API](https://skmtc.dev/corbado/apis/corbado-backend-api.md) · [All operations](https://skmtc.dev/corbado/apis/corbado-backend-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/corbado/corbado-backend-api/revisions/1f6143efe426/schema)