SeaMonkey as a Linux alternative to Mozilla Firefox

Updated October 18, 2026

Our verdict

SeaMonkey is a functional but dated alternative to Firefox. It is not a direct 1:1 replacement for power users who rely on modern web standards or extensive add-on ecosystems. It suits users who want a single, lightweight suite for basic browsing, email, and simple HTML editing without managing separate applications. If you need the latest WebGL support, current extension compatibility, or seamless cross-device sync, stick with Firefox. SeaMonkey is best for minimalists who prefer an all-in-one tool and do not require cutting-edge web rendering.

Feature parity60%

License: MPL-2.0
Price: Free
Latest version: 2.53.24
Rating: —

Install SeaMonkey

What works the same

Both are free, open-source browsers based on the Gecko engine.
Both support tabbed browsing and standard bookmark management.
Both include built-in password managers and cookie controls.
Both allow customization of toolbars and themes.

What is different

SeaMonkey lacks native support for the modern Firefox Add-ons ecosystem.
SeaMonkey does not offer built-in, real-time cross-device sync for tabs and history.
SeaMonkey bundles email, news, and HTML editing, which Firefox does not.
SeaMonkey's rendering engine may lag behind Firefox in supporting the latest web standards like WebGL.

Opening your Mozilla Firefox files

SeaMonkey can import bookmarks and passwords from Firefox using standard formats like HTML or CSV. You can export these from Firefox and import them into SeaMonkey. However, browser profiles, extension data, and session states are not directly compatible. You will need to manually recreate your extension setup and re-login to services, as there is no direct profile migration tool between the two.

Switching from Mozilla Firefox to SeaMonkey, step by step

Export bookmarks and passwords from Firefox as HTML or CSV.
Install SeaMonkey from your Linux distribution's package manager.
Import the exported files into SeaMonkey via the settings menu.
Reinstall any essential extensions that are compatible with SeaMonkey.
Configure email accounts and privacy settings in SeaMonkey.

Key features of SeaMonkey

Integrated web browser with tabbed interface
Built-in email and news client
Simple HTML editor (Composer)
IRC chat client (ChatZilla included)
Password manager and cookie controls
Basic download manager
Customizable toolbars and themes

How to install SeaMonkey on Linux

Fedorasudo dnf install seamonkey

openSUSEsudo zypper install seamonkey

Frequently asked questions

Can I use my existing Firefox extensions in SeaMonkey?

No, most modern Firefox extensions will not work in SeaMonkey. SeaMonkey uses an older extension API, so you must find specific add-ons designed for it.

Does SeaMonkey sync my data across devices?

SeaMonkey does not have a built-in, real-time sync service like Firefox Sync. You would need to manually export and import data or use third-party tools.

Is SeaMonkey suitable for heavy web development?

It is not ideal for heavy development due to potential lag in supporting the latest web standards. Its built-in HTML editor is basic and not a replacement for professional IDEs.