To embed YouTube videos in an HTML document, you can use the <iframe> tag with the appropriate YouTube video URL.
Here is an Example Code
<!DOCTYPE html>
<html>
<head>
<title>YouTube Video Embed</title>
</head>
<body>
<h1>My YouTube Video</h1>
<iframe width="560" height="315" src="https://www.youtube.com/embed/VIDEO_ID" frameborder="0" allowfullscreen></iframe>
</body>
</html>
Output

In the example above, replace “VIDEO_ID” with the actual ID of the YouTube video you want to embed. You can find the video ID in the YouTube URL. For example, if the URL of the video is https://www.youtube.com/watch?v=abc123, the video ID is abc123.
The tag determines the dimensions of the embedded video player. You can adjust these values as needed.
Notes: Save the HTML file and open it in a web browser to see the embedded YouTube video on the page.