Every time you see a calendar widget, it should show your personal availability on it.

When we book a flight, you have to cross-reference your personal calendars to make sure you picked the right days.

Why doesn't this ever work this way today?

Each origin is its own pocket universe that knows everything about its universe and nothing about the other ones.

No individual origin has the data to show you your availability in their widget.

And as a user you wouldn't want every origin to have that data.

The friction of deciding to upload your data for such a feature is just too high for any origin ever to prioritize building this feature.

Why don't browsers add it as a feature?

Browsers are too low a pace layer.

It's not clear how to make a one-size fits all widget for this kind of thing that is generally useful.

This kind of functionality should be built in user-land, where more variations can be tried more quickly.

In user-land a swarm of possibilities can be tried, versus a single feature in a coherent product, which is a consensus swarm.

Browsers would have to add functionality to import availability in some way, and it's not clear how to do it.

Why don't extensions exist to do this?

Presumably some do.

But a user would have to be extremely motivated to choose to find an extension that does this and then install it.

This use case is a minor annoyance for everyone, a major annoyance for no one.

You'd have to trust some random extension author with that data.

And also, the extension would likely inject the information in a way that the origin could read back if it wanted to.

That is, the availability isn't fully isolated from the origin.

This kind of feature is one that we haven't even dreamed could be possible in the same origin model.

Imagine if every experience you interacted with was fully customized to you… and you didn't have to worry about your data flowing out to random sites you didn't like.