# Block a user

`POST /v1/users/{user_id}:block` · permission `users:write`

Blocks a user with a customer block (`source = admin_api`); the status becomes `blocked`. Blocking a user that is already blocked succeeds without a change. A user that is pending deletion cannot be blocked. Revoking the user's sessions runs asynchronously. Send an `Idempotency-Key` header to make retries safe.

## Request

| Parameter | In | Required | Description |
|---|---|---|---|
| `user_id` | path | yes | User id, prefixed `usr_`. |

Optional body:

| Field | Type | Required | Description |
|---|---|---|---|
| `note` | string | no | Up to 1000 characters. Do not write personal data. |

## Response

`200 OK`. The body is the user object. The `ETag` header carries the user version.

Personal data is masked when the key lacks the `users:read_pii` permission: `email` becomes `a***@e***.com`, `phone_number` keeps only its last 2 digits (`+**********67`), `name`, `given_name`, `family_name`, `middle_name` and `nickname` become initials (`A. L.`), `username` keeps only its first character (`a***`), `birthdate` becomes `****-**-**` and `address` becomes `{"redacted": true}`. `user_metadata` and `app_metadata` are not masked.

```json
{
  "id": "usr_0a1b2c3d4e5f6g7h8j9k0m1n2p",
  "kind": "regular",
  "status": "active",
  "external_id": null,
  "username": null,
  "name": "Ada Lovelace",
  "email": "ada@example.com",
  "email_verified": true,
  "phone_number": null,
  "phone_verified": false,
  "user_metadata": {},
  "app_metadata": {},
  "created_via": "admin_api",
  "created_at": "2026-01-15T09:30:00Z",
  "updated_at": "2026-01-15T09:30:00Z",
  "last_sign_in_at": null,
  "deletion_requested_at": null,
  "deletion_due_at": null
}
```

## Errors

Every error is an `application/problem+json` body with a stable `code`.

| HTTP | `code` | When |
|---|---|---|
| 400 | `malformed_request`, `unknown_field` | The body is not valid JSON or has an unknown field. |
| 409 | `conflict` | The user is pending deletion (`errors[].code` is `user_pending_deletion`). |
| 415 | `unsupported_media_type` | A body was sent without `Content-Type: application/json`. |
| 422 | `validation_failed` | `note` is too long. |
| 404 | `not_found` | The user does not exist in this environment (or the id is malformed). |
| 401 | `unauthenticated` | The API key is missing, invalid or revoked. |
| 403 | `insufficient_permissions` | The key lacks the `users:write` permission. |
| 429 | `rate_limited` | The rate limit was exceeded; honor `Retry-After`. |
| 503 | `service_unavailable` | A dependency is temporarily unavailable; retry later. |

## Example

```bash
curl -X POST https://api.eu.keenauth.com/v1/users/usr_0a1b2c3d4e5f6g7h8j9k0m1n2p:block \
  -H "Authorization: Bearer $KEENAUTH_SECRET_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{"note": "Suspected account takeover"}'
```

## Personal data

This endpoint carries personal data: end-user profile. [Personal data in the KeenAuth APIs](/docs/policies/personal-data) describes what is stored, how long it is kept and how it is deleted. Do not send special categories of personal data (health, biometric data, religion, political opinions, sexual orientation) in any field.