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SeaMonkey vs Vivaldi: catalog facts
SeaMonkey	Vivaldi
Free The software is free under its open-source licence. Hosting, hardware and external…	Free Free, funded by default search engine and bookmark placement deals.
Windows, macOS, Linux	Windows, macOS, Linux, Android, iOS
It is the continuation of the old Mozilla Application Suite, so browsing, mail, news and page editing live…	Tab stacking, tiling and vertical tabs without a single extension Built-in mail, calendar and feed reader in a side panel
It tracks an older Firefox codebase, so web compatibility and security hardening trail the current browsers.	Not open source; only the modified Chromium parts are published The sheer number of settings takes real time to work through
Downloadable app	Downloadable app
Open source	Closed source
License: MPL-2.0	License not stated
Not stated if an account is needed	No account needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked September 21, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.