Cyberneura

Mullion

A frameless browser window for leaving a page playing.

Mullion opens a URL or a local file in a window with no visible browser UI, just the page. The navigation bar appears when you ask for it and gets out of the way again. It can run a script after the page loads, and it can live in the menu bar instead of the dock.

Download the latest version

On macOS you can also install it with Homebrew:

brew install --cask cyberneura/tap/mullion

v0.3.1 · 2026-10-11 · Release notes

Supported OS: macOS

github.com/cyberneura/mullion

Features

  • The only chrome shown by default is a 30px title bar holding the window buttons, the favicon, and the title
  • Runs JavaScript or Playwright-compatible code after the page loads (--js / --playwright)
  • Menu bar mode (--menubar), always on top (--always-on-top), and reopening the previous session (--restore)
  • Several targets open as several tabs, and HTML can be read from standard input

Requirements & notes

  • The cask installs Mullion.app only, so options are passed through open -a Mullion --args ....
  • Open source under the MIT License.