Fix a cURL connection timeout

In this article we explain more about fixing the error messages below:

- cURL error 28: Connection timed out after X milliseconds
- cURL error 28: operation time out after X milliseconds with 0 out of 0 bytes received

In most cases the problem is related to the server. It is never actually caused by a plugin or theme in WordPress.

Wat is cURL?


CURL is a command-line program for obtaining or sending files and data.

Because cURL uses libcurl, it supports a range of commonly used Internet protocols, including (currently) HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, LDAP, DAP, DICT, TELNET, FILE, IMAP, POP3, SMTP, and RTSP (the last four are only supported in versions newer than 7.20.0 or 9 February 2010).

CURL supports HTTPS and performs standard SSL certificate verification when a secure protocol such as HTTPS is specified. When cURL connects to an external server via HTTPS, it will obtain the certificate from the external server and then compare the validity of the external server with its CA certificate to ensure that the external server is the server that it claims to be.

cURL is used by the bol.com API, among others, since privacy sensitive information is shared here over an HTTPS connection. That is why bol.com also requires a minimal cURL version.

How do you fix it?


Start with updating WordPress to the most recent version, if you have not already done so.

If the problem persists after updating WordPress, contact your hosting provider and ask them to look at the following parameters:
  • Make sure the server uses the most recent cURL version
  • Try increasing the "WP_MEMORY_LIMIT" at the server level
  • Check if the hosting provider uses an 'openDNS'
  • Check whether the hosting provider has set a limit on the execution of cronjobs
  • Check whether the hosting provider uses a firewall that blocks a cURL request

Need help?


If you cannot find a solution with your hosting provider or if you have additional questions about the cURL error, please contact us at 020 - 225 19 80 or support@woosa.nl.

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