Disable reader view

You posted your question in the macOS community so I'll assume your question pertains to Safari on the Mac. There is a setting in Safari > Preferences > Website > Reader that you can use to automatically open a website in Reader View. This is something that you can turn off:

No. If you don't click the reader view symbol when it appears in the Safari address bar or keystroke ⇧⌘R, then you have implicitly disabled it.