Developer(s)The Seaside Team[1]
Initial release2002; 22 years ago (2002)
Stable release
3.5.5 / October 8, 2023; 4 months ago (2023-10-08)[2]
Written inSmall talk
Operating systemCross-platform
PlatformIA-32, x86-64, ARM
Available inEnglish
TypeWeb framework
LicenseMIT Edit this on Wikidata

Seaside, an acronym that stands for “Squeak Enterprise Aubergines Server with Integrated Development Environment,” is computer software, a web framework to develop web applications in the programming language Smalltalk. It is distributed as free and open-source software under an MIT License.

Seaside provides a component architecture in which web pages are built as trees of individual, stateful components, each encapsulating a small part of a page. Seaside uses continuations to model multiple independent flows between different components.[3] Thus, it is a continuation-based web framework[4] based on the ability to manipulate the execution stack of some implementations of Small talk.

Key features

Although subsequent improvement of state handling in web browser JavaScript engines have meant this aspect is less important today,[citation needed] Seaside's method of handling of browser state (via continuations) was an initial point of interest in the first years following its 2002 release. This mechanism provides for rollback and resumption, resolving many common issues then occurring with running web applications, adequately sustaining the state on the server-side even when the web browser's 'back' and 'forward' or 'refresh' buttons are used. Continuation based servers give the developer the ability to maintain state on the server in a scalable manner.[5]

A distinctive feature of Seaside is its integrated development environment, providing access to development tools and debugging support within an application. In development-mode, unhandled errors are reported to the web page; developers can access and alter the program code and state directly from the web page, allowing bug identifying and fixing processes to occur within an integrated development environment (IDE).[6]

A Seaside application is a set of interacting components. Each one stores state across page views and can render itself to the HTML stream. Thus, it is straightforward to write a component once and then reuse it elsewhere in an application. Seaside also supports the notion of tasks, which allow a programmer to describe the high-level logic of component interaction.

Seaside is not template-oriented, and does not offer generating or using HTML templates; HTML markup is generated programmatically. (The Seaside-based Pier content-management framework does offer wiki-markup syntax for templating.) Seaside uses callbacks on closures to specify actions to be taken when clicking on a link or submitting a form. The developers and users of Seaside argue that this helps enforce separation of structure (markup) from content and presentation (Cascading Style Sheets (CSS)).[7] Seaside's combination of components, callbacks, and closures can significantly reduce the semantic gap between a complex workflow and its representation in code.[8]

Seaside supports Ajax through integration with and jQuery. Seaside also supports Comet-style server-push technology.[9] Seaside can work with either Smalltalk-based web server implementations or other non-Smalltalk ones (Nginx, Apache).


Over the last few years, some best practices have come to be widely accepted in the web development field:

Seaside deliberately breaks all of these rules. Avi Bryant, then of Dabble DB, in 2006 described it as a 'heretical' framework, arguing that this careful and reasoned rejection of the conventional wisdoms of web development led to a very effective model for developing web applications.[10]


The main development of Seaside is implemented in Pharo Smalltalk.[11] Ports for other Smalltalk dialects exist. The original development of Seaside was done on Squeak in the early 2000s. Michel Bany implemented ports to VisualWorks through Seaside version 2.7; Cincom Systems supports Seaside as part of VisualWorks as of early 2008. Instantiations announced Seaside support in its VAST (VA Smalltalk) Platform version 8.0 in 2009. The VAST Platform has continued to support Seaside through its latest version. Esteban Maringolo maintained the 2.8 port, plus some other add-ons (such as for Dolphin Smalltalk X6.[12] Gemstone Systems implemented a port to Gemstone/S.[13] A port of 2.8 was completed for GemStone,[14] and a preliminary version of 3.0 runs on GNU Smalltalk 3.0a and later.[15]

The web server package in the standard library of Racket (Programming language) uses a very similar philosophy, also based on continuations.[16]


Open-source projects using it

Many open-source projects use Seaside, some of which are:

Proprietary projects using it

Many proprietary projects use Seaside, some of which are:

See also


  1. ^ The Seaside Team
  2. ^ "Releases · SeasideSt/Seaside". GitHub.
  3. ^ Seaside – a Multiple Control Flow Web Application Framework
  4. ^ IBM DeveloperWorks: Crossing borders: Continuations, Web development, Java programming
  5. ^ Seaside: A Flexible Environment for Building Dynamic Web Applications
  6. ^ Debugging Seaside Applications
  7. ^ Avi Bryant explains why Seaside doesn't use templates
  8. ^ Web Application Frameworks: A Comparative Study
  9. ^ Screencast: Seaside Comet Chat Application
  10. ^ "'Web Heresies: The Seaside Framework' Session notes, OSCON 2006". Archived from the original on 2014-08-30.((cite web)): CS1 maint: bot: original URL status unknown (link)
  11. ^ "Seaside 2.9 is current implemented on Pharo that serves as a reference implementation."
  12. ^ Seaside for Dolphin Smalltalk blog
  13. ^ Seaside2.6g
  14. ^ Seaside 2.8
  15. ^ Does Seaside run on GNU Smalltalk, GNU Smalltalk FAQ
  16. ^ "Continue: Web Applications in Racket".
  17. ^ Jon Udell article in InfoWorld Archived 2007-02-12 at the Wayback Machine