How to change hosts for your PW site with almost no downtime [for cPanel hosts]

[Violet]

This tutorial is largely to remind myself of the sequence of steps, but if this helps someone else too, that's wonderful!

I've recently moved several PW sites to another host, and I've been refining the order of steps to minimize downtime. Please note, this tutorial is for those moving a site from one host to another host, NOT for local computer to live host (although certainly the same general principles apply). This is written from the point of view where both web hosts have cPanel - for convenience I only use hosts which have cPanel.

The nameservers are one of the last changes you'll make, so don't do that yet!

1. In the old host, go to phpMyAdmin and export the database to your local computer.
2. In File Manager, export your website files as a zip and save to your local computer.
3. Do the same for your email files (e.g. inbox and sent folder). Please note that if you get a lot of email coming through, and/or if you do not plan to complete all the following steps quickly, you might need a more sophisticated solution so as not to miss emails while switching over.
4. Think about what you want your new db, db user, and db password to be (I like to change all this for security reasons). Even if you wished to keep these identical, you couldn't, because your new host will automatically force a different prefix for the db and db user, so you'll wind up with a new db and db user name anyway. The next steps are all done in the new host.
5. In MySQL Databases in the new host, create a new database, db user, and user password from what you decided above. Also, still in MySQL Databases, add that user to the database (this is surprisingly easy to forget).
6. In phpMyAdmin, import the database you exported from before into your freshly created empty database.
7. If your domain name is NOT the main domain name of your new hosting account, create the new domain using Add-on Domains. Otherwise, move on.
8. Go to the main directory for that domain (if your domain is the main domain of your hosting account then public_html, otherwise the folder of your new add-on domain), and upload your zipped website files there and unzip.
9. Go to site/config.php and edit dbname, db user, and user password so that they match the new ones you set up.
10. At this point, be sure you at least have a plan for SSL before moving forward. If your host does AutoSSL that's probably the easiest, at least to get started. If not, or if you're doing e-commerce, look into purchasing a new SSL cert that fits your requirements, either through your host or via a 3rd party if your host allows installation of 3rd party SSL certs. Just as importantly as minimizing downtime, you'll also want to minimize the time your site is without SSL.
11. Then, and only then, change your domain's nameservers at your domain name registrar to point to the new host. Once this change is live, set up SSL right away - however you want to do that is up to you. For cPanel hosts running AutoSSL, just go to SSL/TLS Status and click on "Run AutoSSL" - wait until that domain's status turns green, it could take several minutes.
12. Finally, set up your email on the new host and move the mailbox folders over (don't forget the "sent" folder!)

Optional: If you have Softaculous (which I highly recommend for its auto backup capabilities), go into Softaculous, go to "ProcessWire" and click on "Import" and go for the local option not the remote one. Select your site in the fields and it will automatically import your PW installation. Then to set auto backup schedule, still in Softaculous, go to "all installations" at the top right menu, then on your list of installations go to "edit" (the pencil symbol) next to your new domain's installation. Leave all details the same except for "Automated backups" - select your desired backup rotation options and then click "Save installation details".

Edited January 24, 2021 by Violet
More level of detail for Softaculous