It's time to lazy load offscreen

iframes ?

— , . , , . , , JavaScript , .

Chrome iframe Data Saver, , 2-3% , 1-2% First Contentful Paint 2% (FID) 95- .

?

loading , . :

• lazy .
• eager . .
• auto , .

loading iframes :

<!--   iframe -->
<iframe src="https://example.com" 
        loading="lazy" 
        width="600" 
        height="400"></iframe>

<!--  iframe   -->
<iframe src="https://example.com" 
        width="600" 
        height="400"></iframe>

<!--   loading="eager"      
lazy-loading   Lite Mode -->
<iframe src="https://example.com" 
        loading="eager" 
        width="600" 
        height="400"></iframe>

loading , , (Lite Mode), Chrome auto, , .

iframe JavaScript, iframe.loading = 'lazy':

var iframe = document.createElement('iframe');
iframe.src = 'https://example.com';
iframe.loading = 'lazy';
document.body.appendChild(iframe);

iframe

loading , , , . ( iframe .)

Chrome , iframe :

• iframe 4 .
• display: none visibility: hidden
• iframe X Y
• loading = lazy, loading = auto.

iframe - , Chrome .

, , , . Chrome ,

iframe?

, . :

YouTube ( ~ 500 ):

<iframe src="https://www.youtube.com/embed/YJGCZCaIZkQ"
        loading="lazy" 
        width="560" 
        height="315" 
        frameborder="0" 
        allow="accelerometer; autoplay; 
        encrypted-media; gyroscope; 
        picture-in-picture" 
        allowfullscreen></iframe>

iframe YouTube Chrome.com, 10 , . YouTube, loading = lazy .



YouTube , YouTube lite.

Instagram (> 100 ):

Instagram , iframe . iframe , . , , iframe.

Spotify ( 514 )

<iframe src="https://open.spotify.com/embed/album/1DFixLWuPkv3KT3TnV35m3" 
        loading="lazy"
        width="300" 
        height="380" 
        frameborder="0" 
        allowtransparency="true" 
        allow="encrypted-media"></iframe>

, , .

Facebook

Facebook Facebook -. , , , , … « » — , «» . Like - ( FB JSSDK) ~ 215 , 197 — JavaScript. , , , .

(Stoyan Stefanov) Facebook iframe. , , , , , . , , , . , , iframe .

, ?

, , . Chrome 77 , Lite Mode ( ) Chrome Android.

Lite Mode , . , .

, , navigator.connection.saveData, API NetworkInformation.

-? —

iframe . , loading=«lazy» iframes, iframe , , .

iframes JavaScript lazysizes. , :

• , ,
• iframe :
  
  
  
  

  <script src="lazysizes.min.js" async></script>
  <iframe frameborder="0"
      class="lazyload"
      allowfullscreen=""
      width="600"
      height="400"
      data-src="//www.youtube.com/embed/ZfV-aYdU4uE">
  </iframe>

, :

<iframe frameborder="0"
	  class="lazyload"
    loading="lazy"
    allowfullscreen=""
    width="600"
    height="400"
    data-src="//www.youtube.com/embed/ZfV-aYdU4uE">
</iframe>

<script>
  if ('loading' in HTMLIFrameElement.prototype) {
    const iframes = document.querySelectorAll('iframe[loading="lazy"]');

    iframes.forEach(iframe => {
      iframe.src = iframe.dataset.src;
    });

  } else {
    // Dynamically import the LazySizes library
    const script = document.createElement('script');
    script.src =
      'https://cdnjs.cloudflare.com/ajax/libs/lazysizes/5.2.2/lazysizes.min.js';
    document.body.appendChild(script);
  }
</script>

Built-in lazy loading iframe support makes it much easier to improve the performance of your web pages. If you have any feedback on lazy-loading loading an inline iframe, feel free to post to the Chromium Bug Tracker .

Thanks to Addy Osmani for the article. If you are interested in a deeper dive into the tag iframe bring to your attention an article A comprehensive guide to the tag iframe