Mozilla Firefox vs Opera in 2026

Firefox and Opera are two of the oldest names in browsers, and they ended up in very different places. Firefox stayed independent, kept its own engine and published every line of code. Opera moved to Chromium in 2013, closed its source, changed owners, and now competes on how much it builds in. Comparing them is mostly a question of whether you value openness or convenience more.

Engine and openness

Firefox runs Gecko, the last major engine not derived from Chromium or WebKit. It is fully open source and developed by a subsidiary of the non-profit Mozilla Foundation. Opera runs Chromium, so sites behave as they do in Chrome and Chrome Web Store extensions install through Opera's own add-on. It is closed source, and its largest shareholder since 2021 has been Kunlun Tech, a Beijing-based company whose controlling shareholder chairs Opera's board.

That matters for privacy. Firefox scores 4 in our ratings and Opera scores 3. Both block trackers, but Firefox adds fingerprinting protection and containers, which isolate sites' cookies and have been on by default since Firefox 153. Opera has neither. Opera does block ads by default, which Firefox leaves to extensions.

What Opera builds in

Opera's case is that it arrives complete. It has a free VPN with no subscription, a sidebar that pins WhatsApp, Telegram and other messengers beside the page, workspaces, and a split view that, since Opera One R3, tiles up to four tabs. Its AI assistant, Opera AI (formerly Aria), is free and can use your current tab or a group of tabs as context. Opera scores 5 for AI features against Firefox's 3.

Firefox has closed some of this gap. It added a free built-in VPN in Firefox 149: 50 GB a month in a growing list of countries, with a Mozilla account. Like Opera's, it covers browser traffic only. It has vertical tabs, tab groups and a two-tab split view. Its AI features are deliberately optional: since Firefox 148, a single switch in the settings blocks all current and future generative AI features.

Customisation and extensions

Firefox scores 5 for customizability against Opera's 3, and 5 for extensions against 4. Opera has plenty of features, but they are designed Opera's way and you can only adjust them. Firefox exposes a deep configuration layer and still supports the extension features that let content blockers run at full strength, which Chromium's Manifest V3 restricts in Opera.

Both score 4 for speed and 4 for ease of use, and both run on all five major platforms with sync.

Which should you choose?

Choose Firefox if you want an independent engine, auditable code, fingerprinting protection and unrestricted content blockers, and AI features you can turn off with one switch. Add an ad blocker and it does most of what Opera does, with a better privacy record.

Choose Opera if you want everything built in from the first launch: a VPN with no data cap, messaging beside your tabs, four-way split view and a capable free AI assistant, and you are comfortable with a closed-source browser and its ownership.