Youtube iframe "loop" doesn't work

Try adding the playlist parameter along with the loop. For playlist, set it's value as the current video id.

<iframe class="embed-responsive-item"id="ytplayer" type="text/html" width="640" height="360" src="https://www.youtube.com/embed/M7lc1UVf-VE?&autoplay=1&loop=1&rel=0&showinfo=0&color=white&iv_load_policy=3&playlist=M7lc1UVf-VE"
      frameborder="0" allowfullscreen></iframe>

Currently, the loop parameter only works in the AS3 player when used in conjunction with the playlist parameter. To loop a single video, set the loop parameter value to 1 and set the playlist parameter value to the same video ID already specified in the Player API URL:

http://www.youtube.com/v/VIDEO_ID?version=3&loop=1&playlist=VIDEO_ID

Reference:https://developers.google.com/youtube/player_parameters#loop

i just figure out: you need to have playlist="" to use loop

src="https://www.youtube.com/embed/peSfCy7HFrM?playlist=peSfCy7HFrM&loop=1;rel=0&autoplay=1&controls=0&showinfo=0" frameborder="0" allowfullscreen>

Using in react native like this, make sure to use same video ID value for playlist as well.

for e.g if video id is SpongeBOB then url will be like this :

https://www.youtube.com/embed/SpongeBOB?playlist=SpongeBOB&loop=1

below is implementation in react native webview

<WebView
  javaScriptEnabled={true}
  domStorageEnabled={true}
  mediaPlaybackRequiresUserAction={true}
  style={{ height:180, width:300,alignSelf:"center",alignContent:"center"}}
  source={{uri: 'https://www.youtube.com/embed/qD101Xlc5uw?playlist=qD101Xlc5uw&loop=1' }}
 />