# 40106: No valid authentication method provided

Identifier: `no_valid_authentication_method_provided`



The Ably SDK was given no usable way to authenticate: no API key, token, or token-request mechanism such as authCallback or authUrl was provided.

## What you should do

Configure the client with a way to [authenticate](https://ably.com/docs/auth.md). Set one of `key`, `token`, `authUrl`, or `authCallback` in the client options. For browser and mobile clients prefer `authUrl` or `authCallback`; for server-side use an API `key`.

## Why it happens

The SDK was instantiated without any usable authentication option, so it had no API key, no token, and no means to obtain one. This is a configuration error raised by the SDK before it contacts Ably.

## What you'll see

The error is reported with code 40106 and HTTP status 401. The message is typically `No authentication options provided` or `authOptions must include valid authentication parameters`.