Sometimes I hear "Safari is the new IE" in discussions about support for web platform features. Often, this is said because Safari happens to be the one browser where feature x can't be used. In a practical sense, the feature may indeed even be "available" (and more and more → features are). But that doesn't matter if support for it isn't good enough.
If we separate "available" and "widely supported", we can see more clearly see what's going on here.
Browser updates
Browsers tend to update in one of two ways:
- On their own, independently of things around them
- With the OS
Safari is the odd one out here. It updates with the OS. This means that new web platform features only come when update your OS. While Apple users tend to be quite fast upgrading to the latest version, they'll never be as fast as someone who doesn't even know that they've been upgraded to the latest version automatically.
The long tail of old iOS versions stretches on for a far longer time than that of any other browser. If often becomes the sigular thing we have to wait for when looking at caniuse.com →. Upgrading your OS can be kind of tedious and time-consuming, so it makes perfect sense that some 5% will still be one a version that doesn't support that CSS feature you'd like to use. The percentage tends to be way too large to argue for not supporting. It seems like this is shifting the "widely supported" milestone by 1-2 years for every feature that comes out.
When the EU forces Apple to allow third-party browser engines, the biggest change will arguably be that it will now be possible to have an auto-updating browser that isn't tied to the OS version on iPhones.
Safari is only "The new IE" in the sense that the Safari that web developers can target is always significantly older than the latest available one.