In this article, we will look into the details of “cURL error 28, loopback request cannot complete on WordPress site”. Bobcares, as a part of our WordPress Support Services offers solutions to every WordPress query that comes our way.

“cURL error 28, WordPress could not complete a loopback request”

WordPress and a number of other web apps transmit and receive data requests over URLs using the PHP module called cURL. Since it is a PHP library, we have to make sure we have the recent version of PHP so that the cURL version will also be up-to-date.

The cURL error 28 is a fairly frequent WordPress REST API problem that can affect a website’s performance and possibly lead it to behave strangely. WordPress manages a variety of API queries using cURL. It is essential to how WordPress functions in the backend. So, if we don’t configure the site correctly, WordPress can’t function properly.

When does the error appear?

WordPress sends and receives data requests via the REST API (a programming approach). If these queries time out, a serious issue titled “The REST API encountered in error” will appear in the Site Health report. We get additional error details when we expand the error, stating:

Error: cURL error 28: Operation timed out after x milliseconds with x bytes received (http_request_failed)

We also notice a problem with the message “Your site could not complete a loopback request”. The following description will appear when we expand on this problem.

The loopback request to your site failed, this means features relying on them are not currently working as expected.’ 

So when the system is unable to fulfill the server’s request for data within the timeout period, we will encounter the cURL error 28 on the WordPress site. There are a number of causes for the cURL to timeout, including the DNS server not functioning properly, which would fail HTTP requests and result in a cURL timeout error in WordPress, or the WordPress firewall plugin denying the REST API request because it considers it to be suspicious behavior.

How to fix cURL error 28 on WordPress?

The two main solutions we advise for fixing the issue include:

• Disable firewall: After temporarily disabling the firewall, go to the site health report. If there is no error, then examine the WordPress firewall logs and find those API requests that causes the error previously. So we can find the origin of the issue or we can configure the firewall settings to not restrict authorized API requests.
• Disable plugins: Deactivating all WordPress plugins is the quickest way to determine which one is causing the problem. After that, check the Site Health report once more to see if the problem has been resolved. If the problem is fixed, we can begin activating each plugin one at a time until the problem recurs.

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Conclusion

In this post, we include details about cURL error 28 and the loopback issue on the WordPress site. We also include the methods from our Support team to fix the issue.