WebKit Prefixing Policy
Over time this strategy has turned out not to work so well. Many websites came to depend on prefixed properties. They often used every prefixed variant of a feature, which makes CSS less maintainable and JavaScript programs tricker to write. Sites frequently used just the prefixed version of a feature, which made it hard for browsers to drop support for the prefixed variant when adding support for the unprefixed, standard version. Ultimately, browsers felt pressured by compatibility concerns to implement each other’s prefixes.
The current consensus among browser implementors is that, on the whole, prefixed properties have hurt more than they’ve helped. So, WebKit’s new policy is to implement experimental features unprefixed, behind a runtime flag. Runtime flags allow us to continue to get experimental features into developers’ hands while avoiding the various problems vendor prefixes had. Runtime flags also make it easier for us to have different default settings between stable builds and preview builds such as Safari Technology Preview.
