Analysis of information sources in references of the Wikipedia article "Vivaldi (web browser)" in English language version.
Extensions, or add-ons, can modify and enhance the capability of a browser. Extensions for Firefox are built using the WebExtensions API cross-browser technology. The technology for extensions in Firefox is, to a large extent, compatible with the extension API supported by Chromium-based browsers such as Google Chrome, Microsoft Edge, and Opera. In most cases, extensions written for Chromium-based browsers run in Firefox with just a few changes.
Vivaldi is built in roughly three layers: 1. Chromium, the foundation for our browser. 2. A lot of backend C++ code to support unique features like Ad blocker and Notes. 3. Our UI for desktop (HTML+CSS+JS) and Android [...] Roughly 92% of the browser's code is open source coming from Chromium, 3% is open source coming from us, which leaves only 5% for our UI closed-source code.