Certbot is an awesome way to make sure your websites are secured with encryption and HTTPS.

It’s considered a best practice to have only 1 canonical version of a URL. But when you do that, you can run into issues where you get certificate mis-match errors. Here is an easy way to fix/prevent that.

sudo certbot certonly  -d originaldomain.com -d www.originaldomain.com

However, if you forgot do add in the www the first time, or if you want to create other subdomains that might answer on the same virtualhost, you’ll need to expand your original certificate.

--expand tells Certbot to update an existing certificate with a new certificate that contains all of the old domains and one or more additional new domains.

sudo certbot certonly --expand -d originaldomain.com -d www.originaldomain.com -d new.originaldomain.com -d new2.originaldomain.com -d new3.originaldomain.com --dry-run

NOTE: use the –dry-run flag for testing if it gives you the correct output without errors then re-run the same command and remove –dry-run from the end.