# Make a custom domain primary

`POST /v1/custom-domains/{custom_domain_id}:make-primary` · permission `custom-domains:write`

Makes the domain the environment's primary custom domain (hosted sign-in links use it); the previous primary is released from that role in the same operation. The domain must be `active`; making the current primary primary again changes nothing. When the environment's issuer is on a custom domain, changing the primary domain changes the issuer and must be scheduled as an issuer migration.

## Request

| Field | Type | Required | Description |
|---|---|---|---|
| `custom_domain_id` | string | yes | Custom domain ID (`cdom_…`). |
| `Idempotency-Key` | header | no | Optional key (16-64 characters) that makes a retried request safe. |
| `If-Match` | header | no | Optional. When given it must match the domain's `ETag` (`412` otherwise). |

No request body.

## Response

`200 OK` with the domain and an `ETag` header.

```json
{
  "id": "cdom_01j9xk3m7q8r2s4t6v8w0y2z4a",
  "hostname": "login.example.com",
  "is_primary": true,
  "status": "active",
  "failure_reason": null,
  "dns_records": [
    {
      "type": "TXT",
      "name": "_akp-verify.login.example.com",
      "value": "idp-verify=3q2-7wEXAMPLEtokenQ9"
    },
    {
      "type": "CNAME",
      "name": "login.example.com",
      "value": "acme.eu.edge.keenauth.app"
    }
  ],
  "certificate_expires_at": "2027-01-04T09:31:12Z",
  "last_checked_at": "2026-10-05T09:31:00Z",
  "next_check_at": null,
  "activated_at": "2026-10-05T09:31:12Z",
  "degraded_since": null,
  "status_changed_at": "2026-10-05T09:31:12Z",
  "created_at": "2026-10-05T09:30:00.123456Z",
  "updated_at": "2026-10-05T09:31:12Z"
}
```

## Errors

| HTTP | code | When |
|---|---|---|
| 404 | `not_found` | The custom domain does not exist or belongs to another environment. |
| 409 | `custom_domain_state_conflict` | The domain is not `active`. |
| 409 | `issuer_change_requires_schedule` | The environment's issuer is on a custom domain; the change must be scheduled as an issuer migration. |
| 412 | `precondition_failed` | `If-Match` does not match the domain's current version. |
| 503 | `service_unavailable` | The environment's issuer information is temporarily unavailable. |
| 401 | `unauthenticated` | The credential is missing, invalid or revoked. |
| 403 | `insufficient_permissions` | The credential lacks the required permission. |
| 429 | `rate_limited` | The rate limit was exceeded; retry after the `Retry-After` period. |

## Example

```bash
curl -X POST https://api.eu.keenauth.com/v1/custom-domains/cdom_01j9xk3m7q8r2s4t6v8w0y2z4a:make-primary \
  -H "Authorization: Bearer $KEENAUTH_SECRET_KEY" \
  -H 'If-Match: "4"'
```