Mozilla Firefox vs Vivaldi in 2026

Both of these are browsers for people who want to change things. Firefox and Vivaldi score highest in our directory for customisability — 5 apiece — but they let you customise different layers, and that is the whole comparison.

Two kinds of customisation

Vivaldi customises the interface. Tab bar on any edge, tabs stacked into groups or tiled side by side, a two-level tab hierarchy, split view, custom keyboard shortcuts and mouse gestures for almost any command, themes down to individual colours. It also brings whole applications inside the browser: a real email client, a calendar, an RSS reader and a notes panel, all in the sidebar. If your complaint about browsers is that the chrome around the page is too rigid, Vivaldi answers it more completely than anything else available.

Firefox customises the engine. Its configuration layer exposes hundreds of settings that govern how the browser actually behaves — network handling, rendering, privacy internals — and its userChrome file lets you restyle the interface with CSS if you are willing to write it. This is deeper but far less accessible: Vivaldi hands you a settings panel, Firefox hands you a toolkit.

Licensing, privacy and extensions

The more consequential difference is licensing. Firefox is fully open source and run by a non-profit. Vivaldi's Chromium core is open but its interface layer is proprietary, and it is a private company. Both have good privacy records and both score 4 in our ratings — Vivaldi blocks ads, trackers and cookie banners by default and includes a free VPN, while Firefox blocks trackers and fingerprinting but leaves ad blocking to extensions. If auditability is what you mean by privacy, Firefox is the only one of the two that qualifies.

Extension support favours Firefox, which scores 5 to Vivaldi's 4, because Firefox still permits the older extension APIs that powerful content blockers depend on. Vivaldi, being Chromium, inherits Manifest V3's limits.

Ease of use favours Firefox too — 4 against Vivaldi's 3. Vivaldi's first launch asks a lot of questions, and its density is genuinely intimidating.

Which should you choose?

Choose Firefox if you want an independent engine, fully auditable code, the best extension support available, and a browser that is comfortable out of the box but will go deep when you ask it to.

Choose Vivaldi if your frustration is with the interface rather than the internals — you want tab stacking, split view, mail and calendar in one window, and a free VPN thrown in. It is the more immediately powerful browser; Firefox is the more trustworthy one.