Source

File: wp-includes/embed.php

function get_oembed_endpoint_url( $permalink = '', $format = 'json' ) {
	$url = rest_url( 'oembed/1.0/embed' );

	if ( '' !== $permalink ) {
		$url = add_query_arg(
			array(
				'url'    => urlencode( $permalink ),
				'format' => ( 'json' !== $format ) ? $format : false,
			),
			$url
		);
	}

	/**
	 * Filters the oEmbed endpoint URL.
	 *
	 * @since 4.4.0
	 *
	 * @param string $url       The URL to the oEmbed endpoint.
	 * @param string $permalink The permalink used for the `url` query arg.
	 * @param string $format    The requested response format.
	 */
	return apply_filters( 'oembed_endpoint_url', $url, $permalink, $format );
}