# Validation timeout
<a name="http-validation-timeout"></a>

HTTP validation may time out if the content isn't available within the expected time frame. To troubleshoot validation issues, follow these steps.

**To troubleshoot validation timeout**

1. Do one of the following to check which domains are pending validation:

   1. Open the ACM console and view the certificate details page. Look for domains marked as **Pending validation**.

   1. Call the `DescribeCertificate` API operation to view the validation status of each domain.

1. For each pending domain, verify that the validation content is accessible from the internet.