curl - Is data encrypted when using the --insecure option?

It will be encrypted but insecure. If you trust the certificate you should add the certificate to your certificate store instead of connecting insecurely.

macOS: sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain ~/new-root-certificate.crt

Ubuntu, Debian: sudo cp foo.crt /usr/local/share/ca-certificates/foo.crt sudo update-ca-certificates

CentOS 6: yum install ca-certificates update-ca-trust force-enable cp foo.crt /etc/pki/ca-trust/source/anchors/ update-ca-trust extract

CentOs 5: cat foo.crt >>/etc/pki/tls/certs/ca-bundle.crt

Windows: certutil -addstore -f "ROOT" new-root-certificate.crt

Yes, the transfered data is still sent encrypted. -k/--insecure will "only make" curl skip certificate validation, it will not turn off SSL all together.

More information regarding the matter is available under the following link:

• curl.haxx.se - Details on Server SSL Certificates