To use font-display with Google Fonts, you include a URL parameter like &display=swap in the URL, like https://fonts.googleapis.com/css?family=Open+Sans&display=swap. If you’re copying code from Google Fonts now, it’s the default, so you get it automatically, but you might want to add it if you have existing URLs to Google fonts lingering around, or you want to change it to something like optional if you prefer that.
Source: https://css-tricks.com/google-fonts-and-font-display/