redacted-mode is an Emacs minor mode to hide your current text.

The easiest way to install redacted is MELPA. You can use package.el:

;; Set up package.el to work with MELPA
(require 'package)
(add-to-list 'package-archives
             '("melpa" . "https://melpa.org/packages/"))
(package-initialize)
(package-refresh-contents)

;; Download redacted
(unless (package-installed-p 'redacted)
  (package-install 'redacted))

Use M-x redacted-mode to enable redacted-mode in the current buffer.

To automatically run commands when redacted-mode is enabled use the provided redacted-mode-hook. Here is an example that automatically makes the buffer read-only when redacted-mode is enabled:

;; Enable `read-only-mode' to ensure that we don't change what we can't read.
(add-hook 'redacted-mode-hook (lambda () (read-only-mode (if redacted-mode 1 -1))))

While working on a completely unrelated task, I wanted to share a screenshot of my current Emacs frame, but not of the actual text contents. And while GIMP’s pixelate filter did the job, I didn’t want to fire up my image manipulation program just to share a picture of a custom theme or some functionality.

I thought that Emacs must have some functionality to hide certain information on the displayed text. I remembered toggle-rot13-mode, but anyone interested in the text could decrypt it rather quickly. So instead, I had a look into its implementation and put my Emacs Lisp hat on to find my own solution.