Just like you can package a Scratch project in a Flash wrapper, you can package your SWF file as an application for Windows or macOS. This is the ultimate standalone app -- it will run on any compatible machine, regardless of whether it has Scratch or Flash. There are a few ways to achieve this.
New versions of Flash Player have disabled the Create Projector menu item that allows for easy conversion. You can work around this by using my tool here that performs the same function.
A second method involves downloading a legacy Flash Player archive from here. This is not recommended as it uses a very outdated version of the player. However, I still provide instructions for the process.
To convert to a macOS app, follow these steps:
• Unzip the downloaded archive
• Unzip the Flash Player app found here:
11_2r202_235_32bit/flashplayer11_2r202_235_mac_sa.app.zip
• Open the app. This may result in an error that it is "damaged" -- it's not actually. Fix it with this tool.
• In the Flash Player, choose File > Open and select the SWF
• Choose File > Create Projector to save the macOS application
The steps on Windows are almost the same.
• Unzip the archive and open:
11_2r202_235_32bit/flashplayer11_2r202_235_win_sa_32bit.exe
• In the Flash Player, choose File > Open and select the SWF
• Choose File > Create Projector to save the EXE