macOSDefaultApps

Set which app opens which file extension, UTI or URL scheme on macOS.

A modern successor to RCDefaultApp, SwiftDefaultApps and duti.

Ships as a macOS app and a CLI (mda). Requires macOS 15+.

App

• Browse types by family, or by app to see everything one app handles
• Change a handler from the dropdown in each row, or pick any app via "Other…"
• Filter across extensions, UTIs and app names (⌘F)
• Covers every type and URL scheme your installed apps declare
• English, Deutsch, Français, Español, Italiano, Português, Nederlands, Polski, 简体中文

CLI

mda get md                          # default handler for .md
mda ls md                           # all candidates, default marked *
mda set com.sublimetext.4 md
mda set com.apple.Safari public.html
mda set com.apple.Mail mailto:
mda dump                            # curated types with handlers (or --json)
mda dump --all                      # every type your installed apps declare
mda save                            # snapshot handlers to ~/.mda/default
mda apply                           # restore the default preset
mda apply work                      # a named preset (~/.mda/work)
mda apply settings.duti             # any duti settings file
mda apply initial                   # undo: the state before mda touched this mac
mda --version

md and .md are extensions, public.html is a UTI, mailto: is a URL scheme. mda classifies the target itself.

Presets

mda save writes the current associations to ~/.mda/, one plain-text file per preset, duti syntax. Put the folder in your dotfiles. It warns when the folder isn't under git.

mda apply restores a preset. Apps that aren't installed are skipped and listed, and the exit code is non-zero so a bootstrap script can react. Re-run it after installing them.

The app has the same thing under Presets, with a preview before anything is written.

The restore point

Before mda changes anything for the first time, it records how the machine already looked. Written once, never rewritten.

mda apply initial                   # put it all back

It isn't a preset and isn't in ~/.mda — it lives in ~/Library/Application Support/mda, because it describes one machine and would be wrong on any other. Keep ~/.mda in your dotfiles; this stays behind. ADR 0002.

duti settings files

mda apply reads them as-is. Three-field lines (bundle-id uti role) work unchanged; the role column is ignored. Two fields mean a URL scheme, like duti -s.

Install

brew tap klabast/tap
brew trust klabast/tap                  # required for third-party taps
brew install --cask macosdefaultapps    # app, with mda bundled in
brew install mda                        # cli on its own

Neither needs Xcode. The app is also on the latest release page.

Build from source:

swift build -c release            # cli: .build/release/mda
scripts/package-app.sh            # app: build/macOSDefaultApps.app

Notes

• The app checks GitHub for a newer release at launch and tells you. It installs nothing; brew upgrade or the release page does that.
• Changing the default browser triggers a macOS consent dialog. It can't be silenced.
• There is no API to remove an association, only to point it somewhere else. LaunchServices clears out stale ones.
• The extension ts is MPEG-2 Transport Stream system-wide, not TypeScript.

License

MIT