Implement Lazy Loading Feature in Blogger with Ease - See Guide Implement Lazy Loading Feature in Blogger with Ease - See Guide - Kefblog Tech Solutions

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Implement Lazy Loading Feature in Blogger with Ease - See Guide

The use of images is very important in every blog posts but on the other hand, they can have severe negative impact on your blog by slowing down it's load time which will definitely give your site a low ranking because an average web visitor would not like to wait long for a site to load when there are other sites listed in search results. 

But then, we can't stop using images in posts so the solution to this is to lazy load all images that are not shown yet when your page loads and those images will start loading when the user is about to scroll them into view. What we'll be looking at is how you can setup this feature on your site using an easy to install plugin called Lazysizes.
If you've ever tested your site on Google Pagespeed Insight, you would have come across the saying "Defer offscreen images". But how do you do that?. The answer is to lazy load.

What's Lazy Load?

Lazy load is a very useful feature that lets you keep offscreen element from getting loaded until it reaches the viewport. From the word "lazy" which means to avoid doing a certain task as much as possible. The Image lazy load technique avoids loading images as long as the user doesn't scroll to them. This will save data and ultimately improve the site loading speed. 

Imagine the pagespeed score on page with lazy load:

And the score on same page but without lazy load:

This is because of the fact that images and videos take up about 70% of an average page size. To lazy load them simply means to drastically improve your site's speed. So there will always be a noticeable improvement on any site that implements the lazy loading features. You should do a speed test of your pages before applying lazy load to see the effect. 

Lazysizes

Lazysizes is a third party plugin that lets you lazy load images easily and efficiently - It handles images in various viewports and also includes the ability to lazy load videos as well. Below is the procedure to install the script on blogger and start enjoying its benefits.

Procedure to Implement Lazy load

  1. Paste the Lazysizes code on every page.
  2. Add class lazy to all the images and videos.
  3. Change src attribute to data-src.
  4. Add a lightweight image as placeholder.

How to Place the Code in Blogger

  • Back up your site template. To do this, go to your blogger account and on the left page click Theme then click Backup template.
  • Edit your theme and Copy the below jQuery lazy script and paste it before the end body tag </body> in your template HTML code. Save your theme.
<script type='text/javascript'>
//<![CDATA[
/*! lazysizes - v5.2.0 */ 
!function(a,b){var c=b(a,a.document,Date);a.lazySizes=c,"object"==typeof module&&module.exports&&(module.exports=c)}("undefined"!=typeof window?window:{},function(a,b,c){"use strict";var d,e;if(function(){var b,c={lazyClass:"lazy",loadedClass:"lazyloaded",loadingClass:"lazyloading",preloadClass:"lazypreload",errorClass:"lazyerror",autosizesClass:"lazyautosizes",srcAttr:"data-src",srcsetAttr:"data-srcset",sizesAttr:"data-sizes",minSize:40,customMedia:{},init:!0,expFactor:1.5,hFac:.8,loadMode:2,loadHidden:!0,ricTimeout:0,throttleDelay:125};e=a.lazySizesConfig||a.lazysizesConfig||{};for(b in c)b in e||(e[b]=c[b])}(),!b||!b.getElementsByClassName)return{init:function(){},cfg:e,noSupport:!0};var f=b.documentElement,g=a.HTMLPictureElement,h="addEventListener",i="getAttribute",j=a[h].bind(a),k=a.setTimeout,l=a.requestAnimationFrame||k,m=a.requestIdleCallback,n=/^picture$/i,o=["load","error","lazyincluded","_lazyloaded"],p={},q=Array.prototype.forEach,r=function(a,b){return p[b]||(p[b]=new RegExp("(\\s|^)"+b+"(\\s|$)")),p[b].test(a[i]("class")||"")&&p[b]},s=function(a,b){r(a,b)||a.setAttribute("class",(a[i]("class")||"").trim()+" "+b)},t=function(a,b){var c;(c=r(a,b))&&a.setAttribute("class",(a[i]("class")||"").replace(c," "))},u=function(a,b,c){var d=c?h:"removeEventListener";c&&u(a,b),o.forEach(function(c){a[d](c,b)})},v=function(a,c,e,f,g){var h=b.createEvent("Event");return e||(e={}),e.instance=d,h.initEvent(c,!f,!g),h.detail=e,a.dispatchEvent(h),h},w=function(b,c){var d;!g&&(d=a.picturefill||e.pf)?(c&&c.src&&!b[i]("srcset")&&b.setAttribute("srcset",c.src),d({reevaluate:!0,elements:[b]})):c&&c.src&&(b.src=c.src)},x=function(a,b){return(getComputedStyle(a,null)||{})[b]},y=function(a,b,c){for(c=c||a.offsetWidth;c<e.minSize&&b&&!a._lazysizesWidth;)c=b.offsetWidth,b=b.parentNode;return c},z=function(){var a,c,d=[],e=[],f=d,g=function(){var b=f;for(f=d.length?e:d,a=!0,c=!1;b.length;)b.shift()();a=!1},h=function(d,e){a&&!e?d.apply(this,arguments):(f.push(d),c||(c=!0,(b.hidden?k:l)(g)))};return h._lsFlush=g,h}(),A=function(a,b){return b?function(){z(a)}:function(){var b=this,c=arguments;z(function(){a.apply(b,c)})}},B=function(a){var b,d=0,f=e.throttleDelay,g=e.ricTimeout,h=function(){b=!1,d=c.now(),a()},i=m&&g>49?function(){m(h,{timeout:g}),g!==e.ricTimeout&&(g=e.ricTimeout)}:A(function(){k(h)},!0);return function(a){var e;(a=!0===a)&&(g=33),b||(b=!0,e=f-(c.now()-d),e<0&&(e=0),a||e<9?i():k(i,e))}},C=function(a){var b,d,e=99,f=function(){b=null,a()},g=function(){var a=c.now()-d;a<e?k(g,e-a):(m||f)(f)};return function(){d=c.now(),b||(b=k(g,e))}},D=function(){var g,m,o,p,y,D,F,G,H,I,J,K,L=/^img$/i,M=/^iframe$/i,N="onscroll"in a&&!/(gle|ing)bot/.test(navigator.userAgent),O=0,P=0,Q=0,R=-1,S=function(a){Q--,(!a||Q<0||!a.target)&&(Q=0)},T=function(a){return null==K&&(K="hidden"==x(b.body,"visibility")),K||!("hidden"==x(a.parentNode,"visibility")&&"hidden"==x(a,"visibility"))},U=function(a,c){var d,e=a,g=T(a);for(G-=c,J+=c,H-=c,I+=c;g&&(e=e.offsetParent)&&e!=b.body&&e!=f;)(g=(x(e,"opacity")||1)>0)&&"visible"!=x(e,"overflow")&&(d=e.getBoundingClientRect(),g=I>d.left&&H<d.right&&J>d.top-1&&G<d.bottom+1);return g},V=function(){var a,c,h,j,k,l,n,o,q,r,s,t,u=d.elements;if((p=e.loadMode)&&Q<8&&(a=u.length)){for(c=0,R++;c<a;c++)if(u[c]&&!u[c]._lazyRace)if(!N||d.prematureUnveil&&d.prematureUnveil(u[c]))ba(u[c]);else if((o=u[c][i]("data-expand"))&&(l=1*o)||(l=P),r||(r=!e.expand||e.expand<1?f.clientHeight>500&&f.clientWidth>500?500:370:e.expand,d._defEx=r,s=r*e.expFactor,t=e.hFac,K=null,P<s&&Q<1&&R>2&&p>2&&!b.hidden?(P=s,R=0):P=p>1&&R>1&&Q<6?r:O),q!==l&&(D=innerWidth+l*t,F=innerHeight+l,n=-1*l,q=l),h=u[c].getBoundingClientRect(),(J=h.bottom)>=n&&(G=h.top)<=F&&(I=h.right)>=n*t&&(H=h.left)<=D&&(J||I||H||G)&&(e.loadHidden||T(u[c]))&&(m&&Q<3&&!o&&(p<3||R<4)||U(u[c],l))){if(ba(u[c]),k=!0,Q>9)break}else!k&&m&&!j&&Q<4&&R<4&&p>2&&(g[0]||e.preloadAfterLoad)&&(g[0]||!o&&(J||I||H||G||"auto"!=u[c][i](e.sizesAttr)))&&(j=g[0]||u[c]);j&&!k&&ba(j)}},W=B(V),X=function(a){var b=a.target;if(b._lazyCache)return void delete b._lazyCache;S(a),s(b,e.loadedClass),t(b,e.loadingClass),u(b,Z),v(b,"lazyloaded")},Y=A(X),Z=function(a){Y({target:a.target})},$=function(a,b){try{a.contentWindow.location.replace(b)}catch(c){a.src=b}},_=function(a){var b,c=a[i](e.srcsetAttr);(b=e.customMedia[a[i]("data-media")||a[i]("media")])&&a.setAttribute("media",b),c&&a.setAttribute("srcset",c)},aa=A(function(a,b,c,d,f){var g,h,j,l,m,p;(m=v(a,"lazybeforeunveil",b)).defaultPrevented||(d&&(c?s(a,e.autosizesClass):a.setAttribute("sizes",d)),h=a[i](e.srcsetAttr),g=a[i](e.srcAttr),f&&(j=a.parentNode,l=j&&n.test(j.nodeName||"")),p=b.firesLoad||"src"in a&&(h||g||l),m={target:a},s(a,e.loadingClass),p&&(clearTimeout(o),o=k(S,2500),u(a,Z,!0)),l&&q.call(j.getElementsByTagName("source"),_),h?a.setAttribute("srcset",h):g&&!l&&(M.test(a.nodeName)?$(a,g):a.src=g),f&&(h||l)&&w(a,{src:g})),a._lazyRace&&delete a._lazyRace,t(a,e.lazyClass),z(function(){var b=a.complete&&a.naturalWidth>1;p&&!b||(b&&s(a,"ls-is-cached"),X(m),a._lazyCache=!0,k(function(){"_lazyCache"in a&&delete a._lazyCache},9)),"lazy"==a.loading&&Q--},!0)}),ba=function(a){if(!a._lazyRace){var b,c=L.test(a.nodeName),d=c&&(a[i](e.sizesAttr)||a[i]("sizes")),f="auto"==d;(!f&&m||!c||!a[i]("src")&&!a.srcset||a.complete||r(a,e.errorClass)||!r(a,e.lazyClass))&&(b=v(a,"lazyunveilread").detail,f&&E.updateElem(a,!0,a.offsetWidth),a._lazyRace=!0,Q++,aa(a,b,f,d,c))}},ca=C(function(){e.loadMode=3,W()}),da=function(){3==e.loadMode&&(e.loadMode=2),ca()},ea=function(){if(!m){if(c.now()-y<999)return void k(ea,999);m=!0,e.loadMode=3,W(),j("scroll",da,!0)}};return{_:function(){y=c.now(),d.elements=b.getElementsByClassName(e.lazyClass),g=b.getElementsByClassName(e.lazyClass+" "+e.preloadClass),j("scroll",W,!0),j("resize",W,!0),j("pageshow",function(a){if(a.persisted){var c=b.querySelectorAll("."+e.loadingClass);c.length&&c.forEach&&l(function(){c.forEach(function(a){a.complete&&ba(a)})})}}),a.MutationObserver?new MutationObserver(W).observe(f,{childList:!0,subtree:!0,attributes:!0}):(f[h]("DOMNodeInserted",W,!0),f[h]("DOMAttrModified",W,!0),setInterval(W,999)),j("hashchange",W,!0),["focus","mouseover","click","load","transitionend","animationend"].forEach(function(a){b[h](a,W,!0)}),/d$|^c/.test(b.readyState)?ea():(j("load",ea),b[h]("DOMContentLoaded",W),k(ea,2e4)),d.elements.length?(V(),z._lsFlush()):W()},checkElems:W,unveil:ba,_aLSL:da}}(),E=function(){var a,c=A(function(a,b,c,d){var e,f,g;if(a._lazysizesWidth=d,d+="px",a.setAttribute("sizes",d),n.test(b.nodeName||""))for(e=b.getElementsByTagName("source"),f=0,g=e.length;f<g;f++)e[f].setAttribute("sizes",d);c.detail.dataAttr||w(a,c.detail)}),d=function(a,b,d){var e,f=a.parentNode;f&&(d=y(a,f,d),e=v(a,"lazybeforesizes",{width:d,dataAttr:!!b}),e.defaultPrevented||(d=e.detail.width)&&d!==a._lazysizesWidth&&c(a,f,e,d))},f=function(){var b,c=a.length;if(c)for(b=0;b<c;b++)d(a[b])},g=C(f);return{_:function(){a=b.getElementsByClassName(e.autosizesClass),j("resize",g)},checkElems:g,updateElem:d}}(),F=function(){!F.i&&b.getElementsByClassName&&(F.i=!0,E._(),D._())};return k(function(){e.init&&F()}),d={cfg:e,autoSizer:E,loader:D,init:F,uP:w,aC:s,rC:t,hC:r,fire:v,gW:y,rAF:z}});
</script>

Lazy Loading Images in Blog Posts & Sidebar

To complete the other three steps
  • Go to one of your Blog Posts under blogger and choose HTML View. You'll find the option at the top left.
  • Now for all the images in your post, find <img opening tag and change the src attribute to data-src then place the below code just after the opening tag (leave a space in between) .
 class="lazy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC"

Example:
blog post image without lazy load
<img border="0" height="266" src="https://2.bp.blogspot.com/-CjOIJgqT8ic/WN086VOm6HI/AAAAAAAAAzo/yVBK_61P5bouPpJXK95AaoqbABJb5xaGACLcB/s320/game001.jpg" width="320" />

blog post image with lazy load
<img class="lazy" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" border="0" height="266" data-src="https://2.bp.blogspot.com/-CjOIJgqT8ic/WN086VOm6HI/AAAAAAAAAzo/yVBK_61P5bouPpJXK95AaoqbABJb5xaGACLcB/s320/game001.jpg" width="320" />

Technical speaking, what we did was that:
We changed src attribute to data-src so that the original image will be ignored and we added a new src with a lightweight image that will be loaded instead. Then we added attribute class="lazy" so that the Lazysizes code will understand that our image is to be lazy loaded - the code will then reverse what we did (by removing the src attribute we added and changing data-src back to src) just before the image gets to view.

If you've one or more videos in your post, look for <iframe tag modify it as you did above for the images.

Save your post and do this for your other posts too. If you've advertising banner in sidebar of your pages, edit its code and add the lazy load features. You can do so by going to your blogger account and from the left menu tap on Layout then look for the banner and click edit.

Now you've successfully implemented the lazy load features on your blog images. Go to Pagespeed Insight and run a speed test again to see the difference. Viola! you'll see a massive increase in your performance score 😯.

Lazy Loading Thumbnail Images

You can also lazy load thumbnail images on Homepage and in popular post widget.
  • Go and edit your blog template code like you did when placing the Lazysizes script. Don't forget to always backup your template before making any changes.
  • Look for the <img tags and do the same thing as you did for blog post images but this time, you won't find the src attribute but expr:src instead, so change this to expr:data-src, save your template and you're done.
Note here that some images may have class attribute defined already, so for this kind of images, you should remove the class="lazy" from the <img code because an HTML tag can not have more than one attribute of the same name. But inside the already defined class attribute of the image, type "lazy" to add the class.

Example:
homepage image without lazy load
<img class='thumb' expr:alt='data:post.title' expr:src='data:post.firstImageUrl' expr:title='data:post.title'/>
homepage image with lazy load
<img class='thumb lazy' src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC" expr:alt='data:post.title' expr:data-src='data:post.firstImageUrl' expr:title='data:post.title'/>
That's it!. You have completely added the lazy loading feature to your blog. Every time you published an article, don't forget to add the required attributes to enable the lazy load feature to work..

See Also: How to Render Images in webp format in Blogger - Serve Images in Next Gen

Also Read: How to Lazy Load External JavaScript File including Disqus Comment

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