How to Install InstantSSL on Plesk

To install an Comodo InstantSSL on plesk you need to do two steps, 1. create a csr then upload it, 2. install the certificate comodo send to you (this is the bit that Comodo’s documentation is crap).

Create a CSR

  • In Plesk go to the domain you want a SSL for
  • ClickSSL certificates
  • Click ‘Add SSL Certificate’
  • The name can be anything but make sure the rest of the fields are filled in correctly. Make sure you select 2048 bits
  • Click Request (you will be redirected back to the certificate index page)
  • Select the certificate you just requested, scroll down and the csr should be shown
  • Go to comodo and upload the csr when they ask for it.

Istall InstantSSL on Plesk

This is the bit that is confusing as the Comodo documentation doesn’t match the files they send you. You should recieve three files:

  • www_domain_com.crt
  • AddTrustExternalCARoot.crt
  • UTNAddTrustServerCA.crt If you have move files read the following but then look at the troubleshooting section as well.

Go back to Plesk and the certificate section.

  • Paste www_domain_com.crt into the certificate textarea
  • Paste AddTrustExternalCARoot.crt into the CA Certificate textarea
  • Paste UTNAddTrustServerCA.crt into the CA certificate textarea directly below the AddTrustExternalCARoot.crt
  • Click send text In plesk go back to the domain overpage, click ‘web hosting settings’ and you should see the certificate you just created.


  • If comodo sent through more than the files listed above paste them into the CA certificate in this order (EssentialSSLCA.crt ComodoUTNServerCA.crt UTNAddTrustServerCA.crt AddTrustExternalCARoot.crt)
  • Check the domain has a exclusive IP address
  • Check the certificate pasted into the textarea are in the correct order
  • Check the comodo support site (even though it is rubbish). Hopefully this has helped a few people as every time I have to install a instantSSL I alsways forget which order to do what.