Read-only / View mode
Toggle a buffer read-only to browse without editing; pager-style Space/Backspace paging and a Word-style View Mode banner.
Toggle a buffer read-only with C-x C-q so it can’t be edited by accident, typing and edit commands are blocked while highlighting, folding, search, and copy keep working.
A file that isn’t writable on disk opens read-only automatically, and the per-file state is remembered. A Word-style View Mode banner docks above the editor with an Enable Editing button (when the file is writable), and while read-only, Space pages down / Backspace pages up like a pager.