Make your browser a Notepad.

Open your browser, or a new tab, and type this into the address bar;

data:text/html, <title>Notepad</title><body contenteditable style="font-size:2rem;line-height:1.4;max-width:60rem;margin:0 auto;padding:4rem;">

Save the resulting text as a HTML, or Web Page. The name varies from one browser to another.

You might not use it all the time, but nice to have it bookmarked and ready to go if you need it.