Instagram embed override code for WordPress, to use the embed iframe instead of Instagram's own oEmbed API endpoint.

instagram-embed.php

<?php
/* 
Plugin Name: Instagram Frame Embedder
Author: Otto
*/

wp_embed_register_handler( 'instagram', '#https?://instagr(\.am|am\.com)/p/([^/]+)#i', 'custom_embed_handler_instagram' ); 

function custom_embed_handler_instagram( $matches, $attr, $url, $rawattr ) { 
  if ( !empty($rawattr['width']) && !empty($rawattr['height']) ) { 
		$width  = (int) $rawattr['width']; 
		$height = (int) $rawattr['height']; 
	} else { 
		list( $width, $height ) = wp_expand_dimensions( 612, 710, $attr['width'], $attr['height'] ); 
	} 

	return apply_filters( 'embed_instagram', "<iframe src='//instagram.com/p/". esc_attr($matches[2]). "/embed/' width='{$width}' height='{$height}' frameborder='0' scrolling='no' allowtransparency='true'></iframe>" ); 
}