> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sublay.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Block User

> Block a user by their ID

Creates a block edge from the acting user (the blocker) to the specified user (the target). Blocking is **non-disclosing** — the blocked user is never notified and can never tell they've been blocked.

On a **new** block, Sublay retroactively tears down the existing relationship between the two users in one transaction: any follow in either direction is removed, and any connection or pending connection request in either direction is removed. Nothing is restored on unblock. See [Block enforcement](/sdk/moderation/overview#blocking) for the full list of what a block prevents and hides.

<Note>
  **Requires the `moderation` bundle.** Blocking ships with reporting and suspensions as part of the trust & safety package. A project without the moderation bundle returns `403 database/tables-not-available`. See [Bundles](/bundles).
</Note>

## Path Parameters

<ParamField path="userId" type="string" required>
  The Sublay user ID (UUID) of the user to block (the target).
</ParamField>

## Body Parameters

<ParamField body="actingUserId" type="string">
  The user performing the block (the blocker). Only service/master keys may supply an `actingUserId` other than the caller's own; with a user token the blocker is derived from the token and this field is ignored.
</ParamField>

## Response

On a **new** block, returns HTTP `201` with the created block record. Re-blocking an already-blocked user is an idempotent success and returns HTTP `200` with the existing record.

<ResponseField name="id" type="string">
  Unique block record ID (UUID).
</ResponseField>

<ResponseField name="blockerId" type="string">
  ID of the user who created the block (the acting user).
</ResponseField>

<ResponseField name="blockedId" type="string">
  ID of the user being blocked (the target).
</ResponseField>

<ResponseField name="createdAt" type="string">
  ISO timestamp of when the block was created.
</ResponseField>

## Error Responses

<AccordionGroup>
  <Accordion title="Self-Block — 400">
    ```json theme={null}
    {
      "error": "A user cannot block themselves.",
      "code": "block/self-block"
    }
    ```
  </Accordion>

  <Accordion title="User Not Found — 404">
    ```json theme={null}
    {
      "error": "One or both users involved in the block do not exist.",
      "code": "block/user-not-found"
    }
    ```
  </Accordion>
</AccordionGroup>

## See Also

* [`useBlockManager` hook](/hooks/blocks/use-block-manager)
* [Unblock User](/api-reference/users/blocks/unblock-user)
* [Get Block Status](/api-reference/users/blocks/get-block-status)
* [Block data model](/data-models/block)