How to make the text of the webpage copyable

I recently encountered a requirement that the user wants to copy all the content on the web page, because he found that only the content in the input box can be copied, and the content in the form or other span tags cannot be copied, which is very inconvenient. It is also very simple to change this, just record it for fear of forgetting in the future:

after setting this way, you can copy the content of the whole page! ! ! come on, workman