# [REST API](https://zerossl.com/documentation/api "ZeroSSL Documentation") Validate CSR

## Validate certificate signing request (CSR)HTTPS POST

You might want to validate a certificate signing request (CSR) e.g. before using it in a certificate creation request.

**API Request URL:**

```
api.zerossl.com/validation/csr
```

**HTTPS GET Request Parameters:**

| Parameter     | Description                                                                                         |
|---------------|-----------------------------------------------------------------------------------------------------|
| `access_key` | `access_key` **[Required]** Use this parameter to specify your API access key.                   |

**HTTPS POST Request Parameters:**

| Parameter | Description                             |
|-----------|-----------------------------------------|
| `csr`     | `csr` **[Required]** The CSR you want to validate. |

**API Response:**

If your CSR is valid, you will receive the following JSON:

```
{
    "valid": true,
    "error": null,
    "csrResponse": [
        "2048",
        "sigalg=sha256WithRSAEncryption"
    ]
}
```

**Response Objects:**

| Parameter      | Description                                                                                                |
|----------------|------------------------------------------------------------------------------------------------------------|
| `valid`        | `valid` Returns `true` to indicate your CSR is valid, false otherwise.                                    |
| `error`        | `error` Returns `null` in case the CSR was successfully validated, error code and description otherwise. |
| `csrResponse`  | `csrResponse` Returns an array containing the key size and signature algorithm in case the CSR was successfully validated, `null` otherwise. |

[Error codes](https://zerossl.com/documentation/api/error-codes)