YouTube正在从两个服务器提供缩略图。你只需要用你自己的YouTube视频ID替换＜YouTube_Video_ID_HERE＞。如今，由于图像尺寸较小，webP是快速加载图像的最佳格式。

https://img.youtube.comhttps://i.ytimg.com

示例包括https://i.ytimg.com服务器只是因为它更短，没有其他特别的原因。两者都可以使用。

播放机背景缩略图（480x360）：

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/0.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/0.jpg

视频帧缩略图（120x90）

WebP:
Start: https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/1.webp
Middle: https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/2.webp
End: https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/3.webp

JPG:
Start: https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/1.jpg
Middle: https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/2.jpg
End: https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/3.jpg

最低质量缩略图（120x90）

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/default.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/default.jpg

中等质量缩略图（320x180）

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/mqdefault.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/mqdefault.jpg

高品质缩略图（480x360）

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/hqdefault.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/hqdefault.jpg

标准质量缩略图（640x480）

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/sddefault.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/sddefault.jpg

未缩放缩略图分辨率

WebP
https://i.ytimg.com/vi_webp/<YouTube_Video_ID_HERE>/maxresdefault.webp

JPG
https://i.ytimg.com/vi/<YouTube_Video_ID_HERE>/maxresdefault.jpg

为了添加/扩展所给出的解决方案，我觉得有必要注意到，正如我自己遇到的问题一样，实际上可以通过一个HTTP请求抓取多个YouTube视频内容，在本例中是缩略图：

使用Rest Client（在本例中为HTTPFUL），您可以执行以下操作：

<?php
header("Content-type", "application/json");

//download the httpfull.phar file from http://phphttpclient.com
include("httpful.phar");

$youtubeVidIds= array("nL-rk4bgJWU", "__kupr7KQos", "UCSynl4WbLQ", "joPjqEGJGqU", "PBwEBjX3D3Q");


$response = \Httpful\Request::get("https://www.googleapis.com/youtube/v3/videos?key=YourAPIKey4&part=snippet&id=".implode (",",$youtubeVidIds)."")

->send();

print ($response);

?>

我使用YouTube缩略图的方式如下：

$url = 'http://img.youtube.com/vi/' . $youtubeId . '/0.jpg';
$img = dirname(__FILE__) . '/youtubeThumbnail_'  . $youtubeId . '.jpg';
file_put_contents($img, file_get_contents($url));

请记住，YouTube禁止直接从其服务器中包含图像。

我为YouTube缩略图创建了一个简单的PHP函数，类型如下

违约hq默认值MQ默认值sd默认值最大默认值

function get_youtube_thumb($link,$type){

    $video_id = explode("?v=", $link);

    if (empty($video_id[1])){
        $video_id = explode("/v/", $link);
        $video_id = explode("&", $video_id[1]);
        $video_id = $video_id[0];
    }
    $thumb_link = "";

    if($type == 'default'   || $type == 'hqdefault' ||
       $type == 'mqdefault' || $type == 'sddefault' ||
       $type == 'maxresdefault'){

        $thumb_link = 'http://img.youtube.com/vi/'.$video_id.'/'.$type.'.jpg';

    }elseif($type == "id"){
        $thumb_link = $video_id;
    }
    return $thumb_link;}

    function get_video_thumbnail( $src ) {
            $url_pieces = explode('/', $src);
            if( $url_pieces[2] == 'dai.ly'){
                $id = $url_pieces[3];
                $hash = json_decode(file_get_contents('https://api.dailymotion.com/video/'.$id.'?fields=thumbnail_large_url'), TRUE);
                $thumbnail = $hash['thumbnail_large_url'];
            }else if($url_pieces[2] == 'www.dailymotion.com'){
                $id = $url_pieces[4];
                $hash = json_decode(file_get_contents('https://api.dailymotion.com/video/'.$id.'?fields=thumbnail_large_url'), TRUE);
                $thumbnail = $hash['thumbnail_large_url'];
            }else if ( $url_pieces[2] == 'vimeo.com' ) { // If Vimeo
                $id = $url_pieces[3];
                $hash = unserialize(file_get_contents('http://vimeo.com/api/v2/video/' . $id . '.php'));
                $thumbnail = $hash[0]['thumbnail_large'];
            } elseif ( $url_pieces[2] == 'youtu.be' ) { // If Youtube
                $extract_id = explode('?', $url_pieces[3]);
                $id = $extract_id[0];
                $thumbnail = 'http://img.youtube.com/vi/' . $id . '/mqdefault.jpg';
            }else if ( $url_pieces[2] == 'player.vimeo.com' ) { // If Vimeo
                $id = $url_pieces[4];
                $hash = unserialize(file_get_contents('http://vimeo.com/api/v2/video/' . $id . '.php'));
                $thumbnail = $hash[0]['thumbnail_large'];
            } elseif ( $url_pieces[2] == 'www.youtube.com' ) { // If Youtube
                $extract_id = explode('=', $url_pieces[3]);
                $id = $extract_id[1];
                $thumbnail = 'http://img.youtube.com/vi/' . $id . '/mqdefault.jpg';
            } else{
                $thumbnail = tim_thumb_default_image('video-icon.png', null, 147, 252);
            }
            return $thumbnail;
        }

get_video_thumbnail('https://vimeo.com/154618727');
get_video_thumbnail('https://www.youtube.com/watch?v=SwU0I7_5Cmc');
get_video_thumbnail('https://youtu.be/pbzIfnekjtM');
get_video_thumbnail('http://www.dailymotion.com/video/x5thjyz');

// Get image form video URL
$url = $video['video_url'];

$urls = parse_url($url);

//Expect the URL to be http://youtu.be/abcd, where abcd is the video ID
if ($urls['host'] == 'youtu.be') :

    $imgPath = ltrim($urls['path'],'/');

//Expect the URL to be http://www.youtube.com/embed/abcd
elseif (strpos($urls['path'],'embed') == 1) :

    $imgPath = end(explode('/',$urls['path']));

//Expect the URL to be abcd only
elseif (strpos($url,'/') === false):

    $imgPath = $url;

//Expect the URL to be http://www.youtube.com/watch?v=abcd
else :

    parse_str($urls['query']);

    $imgPath = $v;

endif;