# Check DNS and re-validate certificate (/tls-certificates/App_Certificates_check)

`POST /apps/{app_name}/certificates/{hostname}/check`

## Parameters

| Name | In | Type | Required | Description |
| --- | --- | --- | --- | --- |
| `app_name` | path | `string` | Yes | Fly App Name |
| `hostname` | path | `string` | Yes | Certificate Hostname |

## Responses

| Status | Description | Schema |
| --- | --- | --- |
| `200` | OK | `CertificateCheckResponse` |

The full machine-readable OpenAPI spec is available at /openapi.json.