Under the site health status page on a self hosted WordPress site you can get a recommended improvement of “Have a default theme available”. Even though it is a recommended tip, it is important from the point of view of backup and crash recovery.
What is site health status
WordPress introduced this status page in 2019 as part of WordPress core. It it is useful tool for webmasters to get a summary if things are working fine with their wordpress installation. It does cover the main best practices of WordPress installation.
What is the default theme of WordPress
At the end of each year, the good folks at WordPress announce the launch of the next year’s theme. Understandably they are called after the year of launch. The latest default theme is ‘Twenty Twenty-One’. When you install WordPress with default setting, it is this theme which gets installed. This is why it is called the default theme. This theme is installed and used by thousands of websites which is why it becomes the most popular theme. But for many websites, the default theme is too basic which is why it is changed with some other theme. What webmasters usually do is install another theme and then delete all the other theme files including the default theme.
What is the error message and how to resolve it
The message showing on Site Health status page is ‘Have a default theme available’ is because the default theme has been deleted. Any theme prior to Twenty Twenty-One is also a default theme. You should have at least one default theme to remove the message.
After you resolve the issues, this is what you get on screen.
Why is it a good idea to keep a default theme along with your main active theme
WordPress crashes, many times without warning. There are too many different elements coming together here. Your hosting provided, the WordPress core, your active theme made by some developer, the clutch of plugins, again from different developers. Every webmaster faces this situation one time or the other. While carrying out debugging, a default theme is always a good idea as a backup.