Open zentimer.work in Safari
If your default browser is Safari just click the link above
If you have another default browser set (e.g. Chrome) then hold the link above for a few seconds and then click “Copy the link” in the context menu

Open Safari and paste the link as url

Click the “Share” icon in Safari

Click “Add to Home Screen”

Click “Add”

Congratulations! 🥳 Zentimer now is on your home screen

You can drag it to the bottom menu for your convenience
