SeaMonkey as a Linux alternative to Opera

Updated October 18, 2026

Our verdict

SeaMonkey is not a good replacement for Opera if you rely on a modern, fast browser with built-in VPN and ad blocking. It shares Opera's customizable UI and extension support to some degree, but lacks both performance and critical privacy tools. SeaMonkey's browser component is functional but outdated, with slower page rendering and limited security updates. It may suit users who value integrated email and HTML editing over speed and privacy, but most Opera users will find it lacking. Only consider it if you need a legacy-style internet suite and can live without modern protections.

Feature parity40%

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

Install SeaMonkey

What works the same

Both offer customizable toolbars and themes
Support tabbed browsing
Include built-in email clients
Allow extension installation
Provide password and cookie management

What is different

SeaMonkey lacks a built-in ad blocker and VPN
No regular security updates at the level of Opera
Slower page loading due to older rendering engine
Includes IRC chat and HTML editor not in Opera
Opera has a more modern, performance-focused browser

Opening your Opera files

SeaMonkey does not directly open Opera session files or bookmarks in a proprietary format. If Opera exports bookmarks to HTML, SeaMonkey can import them via its import tool. Passwords and settings cannot be directly migrated. Email data from Opera Mail would need manual export to mbox or similar and imported into SeaMonkey's Mail & Newsgroups component. File compatibility is limited and requires manual conversion.

Switching from Opera to SeaMonkey, step by step

Export Opera bookmarks as HTML
Import bookmarks into SeaMonkey via Tools > Import
Manually reconfigure email accounts in SeaMonkey Mail
Install needed extensions from SeaMonkey add-ons page
Copy saved passwords manually, if required
Adjust toolbar layout under Customize

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

Does SeaMonkey have a built-in ad blocker like Opera?

No, SeaMonkey does not include a built-in ad blocker. You must install an extension like Adblock Plus separately, and even then, filtering is less integrated and effective than in Opera.

Can I use SeaMonkey extensions in Opera or vice versa?

No. SeaMonkey uses legacy XUL extensions, which are incompatible with Opera's Chromium-based extension system. Neither browser can run the other's add-ons.

Is SeaMonkey secure enough for daily browsing?

It's usable but not ideal. Updates are infrequent, and the browser lacks modern sandboxing and real-time threat protection. It's less secure than Opera, especially on untrusted sites.