您必须确保 URL 包含 embed 而不是 watch 作为 /embed 端点允许外部请求，而 /watch 端点不允许.

You must ensure the URL contains embed rather watch as the /embed endpoint allows outside requests, whereas the /watch endpoint does not.

<iframe width="420" height="315" src="https://www.***.com/embed/A6XUVjK9W4o" frameborder="0" allowfullscreen></iframe>