# 40101: Authentication failed

Identifier: `invalid_credentials`



The credentials presented were not accepted, for example an API key secret that did not match, an invalid token, or no credentials supplied at all.

## What you should do

Check that the client is presenting valid [credentials](https://ably.com/docs/auth.md). For Basic authentication, confirm the API key is complete and correct; for token authentication, confirm the token is valid and that any client ID configured on the client matches the one the token was issued for.

## Why it happens

The credentials presented were not accepted. Causes include an API key secret that doesn't match, such as a mistyped or truncated key, an invalid or expired token, a signed token request whose MAC doesn't verify, a client ID that doesn't match the token, or no credentials at all.

## What you'll see

The error is reported with code 40101 and HTTP status 401. The message gives the detail, for example `Not authorized` or `Invalid clientId`.