Browser support

u-elements is committed to provide great support for all users and technologies, including older browser versions.

Based on up-to-date statistics from caniuse.com, u-elements currently support 99.89% of all users on Chrome, Edge, Firefox, Firefox for Android, Opera, Safari, Safari on iOS, and Samsung Internet.

Minimum requirements

Browser version	Release date
Chrome 54+	October 2016
Edge 79+	January 2020
Firefox 63+	October 2018
Firefox for Android 147+	January 2026
Opera 41+	October 2016
Safari 10.1+	March 2017
Safari on iOS 10.3+	March 2017
Samsung Internet 6.2+	October 2017

Web features in use

u-elements tracks browser support by monitoring the web features it uses. This is done by analyzing source code with JSHint and cross-referencing the identified features against MDN Browser Compatibility Data and caniuse.com usage statistics. Here are the web features used by u-elements that are not yet fully supported by all browsers:

Feature	Browser support
Element.attachShadow	99.89%
ShadowRoot.mode	99.89%
Node.getRootNode	99.89%
ShadowRoot.activeElement	99.89%
Window.customElements	99.89%
Element.slot	99.89%
:host	99.89%
:host()	99.89%

Content Security Policy (CSP)

u-elements uses constructable stylesheets to inject styles. If the browser does not support constructable stylesheets (iOS 16.3 and older), u-elements will fall back to instead inject an inline <style> element. Be aware that if you enforce a strict Content Security Policy that blocks the style-src-elem directive, these inline <style> elements will be blocked as well and thus cause styling issues for users on iOS 16.3 and older.