Get User's Preferred Language From Browser

A great way to determine a user's preferred language if you aren't able to ask them directly is to look at the language setting for their browser's UI.

We can get this from the instance of Navigator in the user's JavaScript runtime within the browser.

My browser's UI is set to US English, which I can verify like so:

> navigator.language
'en-US'

This is useful for all sorts of things like formatting dates for display:

> const now = new Date();
> Intl.DateTimeFormat(navigator.language).format(now)
'5/14/2026'

Or for formatting other kinds of units for display:

> const milesFormat =
    Intl.NumberFormat(navigator.language, { style: "unit", unit: "mile" });
> milesFormat.format(1500)
"1,500 mi"