If I create a copy of the default theme and customize it, will this theme get upgraded when the default theme is updated?

Thanks.

No modified theme template files will get updated automatically, you will need to manually update these. If you are just updating CSS in your custom files, that is fine so long as you do not touch any templates.

16 hours ago, Jim M said:

No modified theme template files will get updated automatically, you will need to manually update these. If you are just updating CSS in your custom files, that is fine so long as you do not touch any templates.

I've made some changes to some templates. How can I update the theme and verify that it's up to date?

2 hours ago, Donnie95 said:

I've made some changes to some templates. How can I update the theme and verify that it's up to date?

You would want to use the compare tool in the Theme editor to compare against the unmodified template and make the updates accordingly.

5 hours ago, Jim M said:

You would want to use the compare tool in the Theme editor to compare against the unmodified template and make the updates accordingly.

If I download the default theme and select "Upload a new version," will this work too? Then I will just have to edit a few templates, but I won't have to change the colors. I think it might be faster than creating a new copy.

If you download a theme, then upload it ,it will be the same as copying it