WordPress at a glance
filter is not described

pre_determine_locale filter-hook . WP 5.0.0

Filters the locale for the current request prior to the default determination process.

Using this filter allows to override the default logic, effectively short-circuiting the function.

Usage

add_filter( 'pre_determine_locale', 'filter_function_name_2383' );
function filter_function_name_2383( $null ){
	// filter...

	return $null;
}
$null(string/null)
The locale to return and short-circuit, or null as default.

Where the hook is called

determine_locale()
pre_determine_locale
wp-includes/l10n.php 126
$determined_locale = apply_filters( 'pre_determine_locale', null );

Where the hook is used (in WP core)

Does not used.