How to Find Out What WordPress Theme a Site Is Using Step by Step

There are several ways to find out what WordPress theme a site is using:

Check the source code: You can view the source code of a webpage by right-clicking on the page and selecting "View Page Source". In the source code, search for "wp-content/themes/", and you'll see the theme's folder name.
Use a browser extension: There are browser extensions, such as "What Theme Is That" or "Wappalyzer" that can detect the theme and plugins being used on a website.
Use a theme detector website: There are websites such as "What WordPress Theme Is That" or "IsItWP" which allows you to enter a website URL, and it will tell you what theme is being used.
Check the WordPress repository: If you know the name of the theme, you can check the WordPress repository to see if it's a free theme.
Check the website's files: If you have access to the website's files, you can check the style.css file in the theme's folder to find the theme's name and other information.

It's worth noting that some theme developers might change the name of the theme's folder or the theme's name in the style.css file, in this case, the above methods might not work.

It's also important to note that some website owners might choose to hide the theme name and other information, in this case, it might be difficult to find the theme without access to the website's files.