Here is how a beginner can check if their WordPress website has the WP REST API disabled or enabled.
First, make sure you are NOT logged in to your site.
Then, go to the following web address to test it (be sure to change
yourdomain.com to your own website):
The WP REST API is disabled if you get this message at the top of the page:
In Chrome browser, it will look like this:
In Firefox browser, it will look like this:
If, instead, you see other stuff that begins with your website’s name, then the WP REST API is enabled.