What are Feature Flags in Safari?

Per Apple, writing about how people developing web apps and websites can experiment with upcoming web features.

The web is constantly evolving with new features and technologies. It can be exciting to see potential future tools and technologies, and even more exciting to begin experimenting with them before they ship in web browsers.

Safari lets you enable these features using the new Feature Flags settings, which can be opened from the Develop menu by choosing Feature Flags….

Features are organized by topic, like Animation, CSS, JavaScript, Media, and more, making it easy to find related features. They can also be searched by both feature name and status.

When you toggle a feature to a non-default state, its name is displayed in bold.

Important

The default setting for each feature flag is how users will generally experience your content, so make sure your pages gracefully handle the absence of a feature you’ve enabled for development.