Download websites that use LazySizes unveilhooks plugin

About LazySizes unveilhooks plugin

The name gives away nothing, which is fitting, because most of the sites running this plugin were never asked whether they wanted it. The LazySizes unveilhooks plugin arrives bundled inside a theme, a page builder or a starter template, and gets carried onto thousands of sites by people who never learn that it is there.

The plugin extends LazySizes, a lazy loading library for images and iframes, so that the same deferred loading applies to things that are not images: background images set in CSS, embedded video players, third-party widgets, scripts that only matter once the reader scrolls far enough to need them. The technique addresses a specific and measurable problem, which is that a page's slowest elements are usually the ones nobody looks at.

Presence therefore carries a fairly precise meaning. A site running the plugin has, directly or through its template, adopted a performance practice aimed at Core Web Vitals and at third-party embeds in particular. As of October 2026 we detect it on 12,990 sites, and the geography is lopsided in an instructive way. 4,868 of those sites serve Russia, which reflects template and CMS ecosystems in that market shipping the plugin as standard rather than a national preference for performance engineering, and .ru remains the usual suffix.

The detection caveat matters more here than for most libraries. Because the plugin is a small file designed to be concatenated into a larger bundle, any site that minifies and merges its JavaScript can be running it invisibly. We identify it from recognizable file paths and runtime markers, so the visible population is the portion that ships the plugin as a separate asset and the real number is higher. For the same reason no version can be reported, and the parent library is detected separately, so the two counts belong side by side rather than one inside the other.

Available under the MIT license since 2014 and written in JavaScript, the plugin has no vendor, no telemetry and no registry that could count its use, which is exactly why a crawl-based list is the only way to measure it. Performance tooling vendors use the list to find sites already invested in lazy loading. Agencies use it to work out which template families are common in a market, since a bundled dependency fingerprints the builder rather than the buyer. Researchers studying how loading practices actually spread across the web use it because the interesting unit is the population, not the page.