Updated

Technology · Servers

LazySizes

github.com
Open source

LazySizes is a lightweight, feature-rich JavaScript library used for lazy loading images, iframes, scripts, and other resources. It intelligently loads content only when it's about to enter the viewport, significantly improving page load times and reducing bandwidth usage. LazySizes is highly configurable and works without any dependencies, making it an excellent choice for optimizing web performance.

LazySizes belongs toJavaScript librariesPerformancecategories.

114websites

use it — 4.5% of the 2,555 websites we scanned in the last 12 months

#10of 131

tools in its category seen in our scans (we recognize 314)

11public pages

on UptimeCard — open any of them to see how that site is doing

5.76% of all websites we track run LazySizes▲ 0.01 points since 20 Sep

At a glance

UptimeCard's own scans and tests of 2,555 websites · refreshed weekly

How LazySizes sites scoreout of 100 · hover or tap a score for details

40PerformancePooraverage site: 5088AccessibilityGoodaverage site: 8995Best practicesGoodaverage site: 9392SEOGoodaverage site: 92

Page load time

Loads about 82% slower than the average site

LazySizes sites
7.8 s
All sites
4.3 s

Most LazySizes sites load in 4.9–9.8 s. Home page weight: 4.6 MB vs 3.3 MB for all sites. 10 public sites measured.

Who uses it?

Technology and Software is the biggest group

Technology and Software46%
Software as a Service (SaaS)18%
Economic Data and Analysis9%
Educational Resources9%

Share of 11 classified public sites. “× average” compares with all 961 public sites.

How LazySizes sites are built

Closest partners. The number says how many times more often the tool runs on LazySizes sites than on an average website. Hover a partner for its share of sites.

Twitter Ads3×Swiper3×Microsoft Clarity2×jQuery UI2×Funding Choices2×

Stacks we see most. Tools that tend to run together with LazySizes on the same websites. The percentage is the share of all 114 LazySizes sites that run the whole stack.

12 stacks · swipe, drag or use the arrows
#1

LazySizes + Bootstrap + jsDelivr

7%8 of 114 sites
#2

LazySizes + WordPress + Bootstrap + Yoast SEO + Contact Form 7

3.5%4 of 114 sites
#3

LazySizes + WordPress + Yoast SEO + Elementor + Site Kit

3.5%4 of 114 sites
#4

LazySizes + jsDelivr + Varnish + Drupal

3.5%4 of 114 sites
#5

LazySizes + Funding Choices + Google Hosted Libraries

4.4%5 of 114 sites
#6

LazySizes + WordPress + WP Rocket

4.4%5 of 114 sites
#7

LazySizes + WordPress + jsDelivr

3.5%4 of 114 sites
#8

LazySizes + Bootstrap + Funding Choices

3.5%4 of 114 sites
#9

LazySizes + Bootstrap + YouTube

3.5%4 of 114 sites
#10

LazySizes + Funding Choices + Varnish

3.5%4 of 114 sites
#11

LazySizes + YouTube + Drupal

3.5%4 of 114 sites
#12

LazySizes + jsDelivr + Unpkg

3.5%4 of 114 sites

Usually installed alongside

The bigger the bubble, the more of the 114 LazySizes sites also run the tool. Colour shows what the tool does. Hover or tap a bubble for details.

Google Analytics75%Facebook Pixel29%Microsoft Clarity23%Google Tag Manager72%Cart Functionality23%OneTrust18%Funding Choices15%Yoast SEO18%Microsoft Advertising16%Twitter Ads15%
AnalyticsTag managerOnline storeCookie consentSearch visibilityAdvertising

Similar tools in its category

JavaScript libraries: 314 tools known, 131 seen in our scans

Priority Hints755 sitesAlternativeLodash184 sitesAlternativelit-html155 sitesAlternativelit-element128 sitesAlternativeBoomerang96 sitesAlternativeweb-vitals73 sitesAlternativeGoober65 sitesAlternativeLoadable-Components44 sitesAlternativejQuery1,030 sitesUsed togethercore-js776 sitesUsed togetherSwiper285 sitesUsed togetherjQuery Migrate245 sitesUsed together

How websites combine LazySizes with other tools

Relationships found on the websites that use it, from the same map status pages show.

Complements another tool 19Integrates with another 1

Questions about LazySizes

How many websites use LazySizes?
We found LazySizes on 114 of the 2,555 websites we scanned in the last 12 months (4.5%). 11 of them have a public status page.
What is LazySizes often used with?
Among the websites we scan, LazySizes is often found alongside Google Analytics (74.6% of its sites), PHP (39.5% of its sites), Swiper (31.6% of its sites).
What are the alternatives to LazySizes?
Other javascript libraries tools we recognize include jQuery, core-js, Priority Hints, Swiper.

Is your website built with LazySizes?

UptimeCard checks it around the clock, tells you the minute it stops answering, and gives your visitors a status page.

Monitor my site freeCreate a status page