# 40166: Unidentified client cannot modify own messages

Identifier: `unidentified_client_cannot_modify_own_messages`



A message update or delete was rejected because the client is unidentified — it has no clientId — but holds only the "own" form of the relevant capability, message-update-own or message-delete-own, which can never apply to a client that has no messages of its own.

## What you should do

Update the client to set a `clientId`, so it connects as an [identified client](https://ably.com/docs/auth/identified-clients.md) which can own messages that an "own" capability can match; or grant the client the corresponding "any" [capability](https://ably.com/docs/auth/capabilities.md) — `message-update-any` or `message-delete-any` — which permits acting on messages regardless of author.

## Why it happens

The `message-update-own` and `message-delete-own` capabilities only permit a client to change messages it published itself, matched by `clientId`. An unidentified client has no `clientId`, and so no messages of its own, leaving an "own" capability with nothing it is permitted to act on.

## What you'll see

The error is reported with code 40166 and HTTP status 401. The message names the operation and the capability required, for example `Unable to update message: anonymous clients require the 'message-update-any' capability (they cannot have own messages, so 'message-update-own' does not apply)`, and the equivalent for delete with `message-delete-any`.