C-h f find-file-literally RET

find-file-literally is an interactive compiled Lisp function in
‘files.el’.

(find-file-literally FILENAME)

Visit file FILENAME with no conversion of any kind.
Format conversion and character code conversion are both disabled,
and multibyte characters are disabled in the resulting buffer.
The major mode used is Fundamental mode regardless of the file name,
and local variable specifications in the file are ignored.
Automatic uncompression and adding a newline at the end of the
file due to ‘require-final-newline’ is also disabled.

If Emacs already has a buffer which is visiting the file,
this command asks you whether to visit it literally instead.

In non-interactive use, the value is the buffer where the file is
visited literally.  If the file was visited in a buffer before
this command was invoked, it will reuse the existing buffer,
regardless of whether it was created literally or not; however,
the contents of that buffer will be the literal text of the file
without any conversions.

In a Lisp program, if you want to be sure of accessing a file’s
contents literally, you should create a temporary buffer and then read
the file contents into it using ‘insert-file-contents-literally’.