Web-browser, advanced e-mail, newsgroup and feed client, IRC chat, and HTML editing made simple—all your Internet needs in one application.
The SeaMonkey® Project
The SeaMonkey project is a community effort to develop the SeaMonkey Internet Application Suite (see below). Such a software suite was previously made popular by Netscape and Mozilla, and the SeaMonkey project continues to develop and deliver high-quality updates to this concept. Containing an Internet browser, email & newsgroup client with an included web feed reader, HTML editor, IRC chat and web development tools, SeaMonkey is sure to appeal to advanced users, web developers and corporate users.
Under the hood, SeaMonkey uses much of the same Mozilla Firefox source code which powers such products as Thunderbird. Legal backing is provided by the SeaMonkey Association (SeaMonkey e.V.).
Project News
May 1, 2025
SeaMonkey 2.53.21 Beta 1 released
SeaMonkey 2.53.21 Beta 1 is now available for free download on the SeaMonkey website.
2.53.21 will be an incremental update on the 2.53.x branch and incorporates a number of enhancements, changes and fixes to the application as well as those from the underlying platform code. Before installing the new version make a full backup of your profile and thoroughly read and follow the Release Notes. We encourage testers to get involved in discussing and reporting problems as well as further improving the product.
Our Windows signing key expired in January and the way new keys are distributed totally changed last year. We are currently working on acquiring a new key and integrating the new signing process into our infra, but it will take some time to complete. So until we accomplish this, starting with 2.53.21b1, our Windows releases will be distributed unsigned. If you are concerned about the integrity of the downloads please check the binaries against the checksum files we provide.
2.53.21 is planned to be the last version distributed for 32 bit x86 Windows and Linux. We suggest you test the beta to report any regressions which might have crept in so that we can fix them for the final version. The beta should have release quality and the final version can be installed over it.
SeaMonkey 2.53.21 Beta 1 is available in 23 languages, for Windows, macOS x64 and Linux.
January 12, 2025
January 6th, 2025 was a sad day for SeaMonkey and all of us
Our friend, SeaMonkey developer and releng William Andrew Gianopoulos, better known as WG9s, passed away unexpectedly on Monday, January 6, 2025.
Visit his obituary for further details and, if you feel so, add a condolence message.
We are still all very sad and will miss him and his cat Bella much. Light a candle for him and remember: No one is really dead unless you stop thinking about him or her and we won't forget him and what he did for sure.
He left a big hole and we will see what we can do about publishing prerelease builds in the future.
Rest in Peace Bill
January 7, 2025
SeaMonkey 2.53.20 released
The SeaMonkey project is proud to present SeaMonkey 2.53.20: The new release of the all-in-one Internet suite is available for free download now!
2.53.20 is an incremental update on the 2.53.x branch and incorporates a number of enhancements, changes and fixes to the application as well as those from the underlying platform code. We have also added many fixes and backports for overall platform stability.
Please be advised that the minimum requirements for running SeaMonkey under Linux have changed. We are building on Rocky 8 Linux now and the dependencies are picked up from the builder library levels. The new minimum requirements are glibc 2.28, glib 2.56, gtk+2 2.24, gtk3 3.22.30 and pixman 0.36. See Linux compatibility matrix. This only applies for the official binary releases from our server. Distribution specific versions might have different minimum version requirements.
If you are using macOS 15.1.x please update to 15.2. Because of a bug in the OS SeaMonkey can not be started via Finder or Dock without workarounds. This applies to older versions too.
We are aware of numerous websites breaking because of only supporting the latest Chrome or Firefox versions. We are trying to address this and progress has been made in a different source code branch but the code is not ready for general distribution yet.
SeaMonkey 2.53.20 is available in 23 languages, for Windows, macOS x64 and Linux.
Automatic upgrades from previous 2.53.x versions are enabled for this
release, but if you have problems with it please download the full installer
from the downloads section and install SeaMonkey 2.53.20 manually over the
previous version.
For a more complete list of major changes in SeaMonkey 2.53.20, see the What's New in SeaMonkey 2.53.20 section of the Release Notes, which also contains a list of known issues and answers to frequently asked questions. For a more general overview of the SeaMonkey project (and screen shots!), visit www.seamonkey-project.org.
We encourage users to get involved in discussing and reporting problems as well as further improving the product.
November 6, 2022
SeaMonkey and macOS Ventura
Attention macOS users! The current SeaMonkey release crashes during startup after upgrading to macOS 13 Ventura. Until we have a fix we advise you not to upgrade your macOS installation to Ventura. No usable crash information is generated and this might take a bit longer than usual to fix. This is not a problem with Monterey 12.6.1 or any lower supported macOS version so might even be an Apple bug.
The problem is tracked in Bug 1797696.
The SeaMonkey Internet Application Suite
SeaMonkey has inherited the successful all-in-one concept of the original Netscape Communicator and continues that product line based on the modern, cross-platform architecture provided by the Mozilla project.
- The Internet browser at the core of the SeaMonkey Internet Application Suite uses the same rendering engine and application platform as Mozilla Firefox, with popular features like tabbed browsing, feed detection, popup blocking, smart location bar, find as you type and a lot of other functionality for a smooth web experience.
- SeaMonkey's Mail and Newsgroups client shares lots of code with Thunderbird and features adaptive Junk mail filtering, tags and mail views, web feeds reading, tabbed messaging, multiple accounts, S/MIME, address books with LDAP support and is ready for both private and corporate use.
- Additional components include an easy-to-use HTML Editor, the ChatZilla IRC chat application and web development tools like a DOM Inspector.
- If that's still not enough, SeaMonkey can be extended with numerous Add-Ons that provide additional functionality and customization for a complete Internet experience.