[taeric]

And many people are almost certainly going to find that they actually need to either recall an old immutable thing, or mutate it.

Also, I will certainly want to clear out my browser's cache on a regular basis. I do not want it keeping immutable things just because they shouldn't ever change.

[Dylan16807]

You can't 'recall' something you already sent out to browsers, and if you need to mutate then it's easy to make a new URL.

This header won't make browsers cache data any differently. It skips a step when the cache is being read from.

[taeric]

But in the current world, you can serve new content on the conditional check that caches currently do.

That said, I am ultimately for this. I think. There is plenty of data showing that this is a low hanging fruit to hit.

[Dylan16807]

The conditional check that they do sometimes. Now half your users see the new version and half see the old version. Not much of a recall.

[taeric]

Still more of a recall than will be possible in the new world. And you can always detect the old code and prompt users to refresh. (Typically happens on a restart.)

Again, though, I am ultimately for this. I just remain skeptical of any panacea.

[nine_k]

You sound as if people who consciously set an immutable header, or set cache expiration time header to 5 years, do not know what they are doing.

Should we optimize the web for clueless server operators?

[taeric]

With the numbers of folks that fix local development by clearing caches... Yes, I am comfortable claiming that. :)