How to Solve the cURL (60) Error When Using Proxy?

The cURL (60) error is a common error encountered when using proxies with cURL. The full error traceback looks like the following:

curl: (60) schannel: SEC_E_UNTRUSTED_ROOT (0x80090325) - The certificate chain was issued by an authority that is not trusted.
More details here: https://curl.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it.

This error happens when cURL attempts to request a web page over the HTTPs protocol with a proxy server that doesn't have a valid TLS certificate. Hence, it fails to establish a secure connection.

To solve the cURL (60) error, you can use a proxy that has a valid TLS certificate to support the HTTPs protocol. Alternatively, you can omit establishing the secure connection by adding the -k cURL option:

curl -x https://proxy_domain.com:proxy_port https://httpbin.dev/ip -k

For further details on proxies, including their types and best practices when choosing a proxy, refer to our introduction guide.