What is Chromium?
Definition Chromium is the open-source browser project started by Google in 2008 on which Google Chrome is built. Its rendering engine is Blink, a fork of WebKit made in 2013, and its JavaScript engine is V8. Microsoft Edge, Samsung Internet, Opera, Brave and Android System WebView are also based on Chromium, so on Android phones most pages are rendered by Blink.
Try it: Test a website on Android
Chromium, Chrome and Blink
- Chromium is the open-source code base: rendering, networking, the user interface and so on.
- Blink is the part that turns HTML and CSS into pixels. It was forked from WebKit in 2013 and has developed separately since.
- Google Chrome is Chromium plus Google's own additions, such as automatic updates, sync and licensed media codecs.
Other browsers take Chromium and add their own features, but they share Blink, so a layout that works in Chrome on Android almost always works the same in Edge or Samsung Internet. The exception is browser-specific features, such as Samsung Internet's own dark mode, which can recolor pages.
Why Chromium matters for mobile testing
Chromium is the engine behind most Android browsing and behind Google's tools:
- Googlebot renders pages with an up-to-date Chromium, which matters under mobile-first indexing.
- Lighthouse, PageSpeed Insights and Chrome DevTools run on Chromium.
- The Chrome UX Report, the source of Core Web Vitals field data, comes only from Chrome users.
- Some web platform APIs exist only in Chromium, such as the Layout Instability API behind CLS and User-Agent Client Hints.
Chromium on iPhone
Chrome for iPhone is not the same engine as Chrome for Android. Under Apple's rules it uses WebKit for rendering, so a bug that appears only "in Chrome on iPhone" is usually a WebKit bug. Likewise, picking an iPhone in Chrome DevTools device mode only changes the viewport size, pixel ratio and user agent: the page is still rendered by Blink, so Safari-specific behavior can't show up there.
Example: detecting features, not engines
/* Works in any engine that supports it */
@supports (height: 100dvh) {
.app { height: 100dvh; }
}Testing for a feature with @supports is more reliable than guessing the engine from the user agent string.
Chromium in MobileCheck
MobileCheck renders Android phones and tablets in Chromium, with each device's real viewport, pixel ratio and user agent, and iPhones and iPads in WebKit. The Safari vs Chrome comparison renders the same iPhone screen in both engines side by side.