The webcomponentsjs polyfills add custom elements and shadow DOM to older browsers.
7,601 websites in the PageSourceSearch index contain the code that reveals it; the 50 highest-ranked are listed below.
How is Web Components polyfills detected?
The page loads webcomponents-loader.js or webcomponents-bundle.js. The discovery keyword is the exact bytes PageSourceSearch looks for in every stored page and script:
A literal is matched byte for byte, case-sensitively. Combine it with another keyword, a domain, a kind or a date filter on the search page to narrow the list. About Web Components polyfills
Top 50 websites using Web Components polyfills
Ranked by the domain's position in the crawl's ranked list (Common Crawl harmonic centrality), highest first. view source opens the stored page or script with the match highlighted. Computed 2026-09-29 21:16:10 UTC.
How does PageSourceSearch know a website uses Web Components polyfills?
By the source itself: The page loads webcomponents-loader.js or webcomponents-bundle.js. PageSourceSearch stores the raw HTML and first-party JavaScript of each crawled site and matches the keyword byte for byte, so every listed site's stored source contains it.
Is this a complete list of websites using Web Components polyfills?
No. The page lists the 50 highest-ranked sites in the index whose source holds the keyword, out of 7,601 websites that do; the count is the index's estimate at the time the list was computed. Run the keyword as a search to page through all of them, or add a kind or date filter.
How do I find websites that use Web Components polyfills together with another technology?
Search for both keywords at once: several terms separated by spaces must all be found on the same site, or with the Same page toggle in the same page. For example webcomponents-(loader|bundle|lite)(\.min)?\.js with wp-content/plugins/ lists the WordPress sites that use Web Components polyfills.