title: Every YouTube video has two links
body: <p>I've tried playing with YouTube video URL's and found that two every video has two links for example</p>
  
  <p>Suppose a video has  the following link </p>
  
  <p><a href="https://www.youtube.com/watch?v=YykjpeuMNEk" rel="nofollow">https://www.youtube.com/watch?v=YykjpeuMNEk</a></p>
  
  <p>Now I change the last letter of the link to make it </p>
  
  <p><a href="https://www.youtube.com/watch?v=YykjpeuMNEl" rel="nofollow">https://www.youtube.com/watch?v=YykjpeuMNEl</a></p>
  
  <p>Try out both the links would open one video.</p>
  
  <p>The logic is change the last letter with the consecutive letter, the letters are case sensitive.</p>
  
  <p>So if the last letter is 'a' change it to 'b', if 'A' change it to 'B', if '1' change it to '2'.</p>
  
  <p>Can someone explain me what is happening in this case?</p>