Servlets are supported in nearly all web servers, from Apache to Zeus. Some web servers support servlets right out of the box. We call this type of server a Standalone Servlet Engine. Other web servers require a third-party plug-in to support servlets. We call the servlet-enabling plug-in an Add-on Servlet Engine. Finally, if you want to write your own server with servlet support, you can use what's called an Embeddable Servlet Engine.

NEW: I've added a section for JavaServer Pages (JSP) plug-in engines.

This page is a compiled list of the most frequently used servlet engines. If your favorite engine isn't listed, please let me know.

A standalone servlet engine is a server that includes built-in support for servlets. Such an engine has the advantage that everything works right out of the box. One disadvantage, however, is that you have to wait for a new release of the web server to get the latest servlet support.

The Tomcat Server, from Project Jakarta (Updated!)

The open source reference implementation for servlets and JSPs. Always supports the latest Servlet API revision. It's written entirely in Java. Source code is available under the excellent (better than GPL) Apache license as part of Project Jakarta. Version 3.0 has been released. It's undergoing rapid development (you can help out if you'd like) for future versions.

Sun's JavaServer Web Development Kit (JSWDK) (New!)

The previous reference implementation for servlets and JSPs. The code for the JSWDK has been released to become the Tomcat server listed above. You can download the JSWDK 1.0.x release for free and redistribute the class files as part of your product for free as well. It's currently more stable than the Tomcat server which is undergoing rapid development for an upcoming release.

Sun's Java Web Server

The previous (unofficial) reference implementation for how a servlet engine should support servlets. Written entirely in Java (except for two native code libraries that enhance its functionality but are not needed). Free 30-day evaluation. Free educational license. $295 commercial. Officially "end of lifed" in favor of Netscape products due to the Sun-Netscape Alliance.

Caucho's Resin Server (New!)

An Open Source servlet engine that prides itself on performance. Works standalone or coupled with Apache, IIS, or iPlanet/Netscape. It can also be used to add JSP support to any JSDK 2.1 engine. It integrates XML, XSL, and JavaScript inside the engine. Free under the "Open Source" Caucho Public License, although they politely request commercial users pay a license fee.

Oracle Application Server (New!)

Oracle 8i and the Oracle Application Server have built-in support for servlets and a downloadable JSP 1.0 engine. Check out their JDeveloper 2.0 tool if you plan to go this route. No pricing information seemed readily available.

The Sun WebServer

A web server designed to efficiently support thousands of virtual hosts. Works only on Solaris, but includes kernel hacks to improve performance. The just released version 2.1 supports Servlet API 2.0. Available as part of the Solaris ISP Server ($2,485) or Easy Access Server ($595). Both bundles include additional software products. Officially "end of lifed" I believe in favor of Netscape products due to the Sun-Netscape Alliance.

ATG Dynamo Application Server

An application server from ATG (Art Technology Group) written in Java with support for servlets. Free evaluation. Contact for pricing.

BEA Weblogic Application Server

A high-end server written entirely in Java that supports servlets, among other things. Formerly Weblogic's Tengah Application Server. $4,000.

The World Wide Web Consortium's Jigsaw Server

A full-featured web server written in Java that serves as the reference HTTP/1.1 implementation. Free.

O'Reilly's WebSite Pro

The first server not written in Java to provide built-in servlet support. Works with Windows 95 and Windows NT. $799.

Zeus Web Server

The web server commonly considered the fastest available, now with servlet support. $1699 per machine.

iPlanet (Netscape) Web Server Enterprise Edition (New!)

The Sun|Netscape Alliance released the iPlanet Web Server Enterprise Edition (iWS) 4.0. This is the upgrade from Netscape Enterprise Server 3.x. It supports Servlet API 2.1 that should be really good. They're so proud of their servlet implementation that in the FAQ question "Aren't there several freeware contenders?" their answer is "When measured against freeware competitors like Apache and bundled products like Microsoft IIS, iPlanet Web Server 4.0 demonstrates an unparalleled Java implementation and considerable performance advantages". $1495 per CPU.

iPlanet (Netscape) Web Server Enterprise Edition for Linux (New!)

The Sun|Netscape Alliance has an alpha of the iPlanet Web Server Enterprise Edition (iWS) 4.1 for Linux. It supports Servlet API 2.2 (except for WAR files) and JSP 1.1PR1. It's not clear if there are 4.1 alphas for other platforms.

Netscape Enterprise Server 3.5.1 and 3.6 (Updated!)

The most popular web server to provide built-in servlet support. Unfortunately, NES 3.x supports only the early Servlet API 1.0 and suffers from a number of bugs so significant it's almost unusable. Users of NES 3.x should upgrade to iPlanet 4.0 (above) or use an add-on servlet engine. $1295 per CPU.

Inprise Application Server (Updated!)

Inprise Application Server 4 includes support for J2EE including servlets 2.1 and JSP 1.0. Pricing appears to be $895 per developer and $8,500 per CPU for deployment. Check out their corp sales web site for more information. An evaluation download is available.

GemStone/J Application Server (New!)

The GemStone/J Application Server supports Servlet API 2.1 and JSP 1.0. The base technology is New Atlanta's ServletExec, but GemStone/J adds multi-process support and automatic HTTP session state distribution among multiple JVMs running servlets. For pricing, call 800-243-9369 or email info@gemstone.com. If you are quoted a price, let me know and I'll post it here.

Gefion Software's LiteWebServer (New!)

A pure Java web server that (as of 11/21) supports Servlet API 2.2 (PR1) and JSP 1.1 (PR2). It's just 420K (130K without JSP), so it's well suited for embedded systems and bundling with demos. For most uses it can be used free of charge. Source is available with a support license, priced at $149 annually per copy or $1,600 for unlimited copies.

CtO-JStar (New!)

A commerical web server written in Java, announced at JavaOne '99. The company says it "provides linear scalability for Java servlets". There's a whitepaper on its architecture. Supports Servlet API 2.0 with 2.1 coming in the last quarter of '99 along with JSP 1.0. Their slogan is "J-Star, for web sites that must scale and cannot fail". :-) They say to call for pricing and release information.

M5 Web Server

A commerical web server written in Java. Supports Servlet API 2.1 and HTTP/1.1. Its security model is appealing: SecurityManager sandboxes and supports throttling by virtual server (limiting denial of service attacks). I also like its ability to compress output according to configurable rules! 15 day evaluation. Just $95.

Servertec's iServer (New!)

A small web and application server written in Java. Supports Servlet API 2.1 and HTTP/1.1. Can use a database for security controls and server logs. Preview release is free, commercial license is $50, redistribution license is $1,500.

LiveSoftware's JRun Web Server

Although it's best known as a plug-in (see below), JRun also includes a full standalone web server. Lets you run a different virtual machine per virtual host if you need. JRun is free for development, testing, and non-commercial deployment and contains the full feature set of JRun Pro including JSP. JRun Pro is $595 for commercial deployment and features unlimited concurrency.

Lotus's Domino Go WebServer

A popular web server with support for servlets. Works with most platforms. $540.

Mort Bay's Jetty Server

An open source web server written in 100% Java designed to stand alone or be embedded (thus shown again below). Claims support for Servlet API 2.1; includes GNUJSP. No fee for use as it's distributed under the Open Source Artistic license.

Paperclips Java Servlet Server 2.0

A free web server to run servlet. Written in Java; provided with source. Version 2.1 will be GPL'd.

KonaSoft Enterprise Server

A Java application server with support for servlets. $4995 for 100-user version.

EzWebTools Lightweight Servlet Engine (ELSE) (Updated!)

Previously called "JAWS". A free (but not open source) servlet engine that claims to support Servlet API 2.1 and JSP 1.0. Includes a security manager that isolates servlets from one another. Currently in early beta.

Avenida Web Server

A small web server built around the servlet architecture.

vqServer

A small web server written in Java. HTML administration. Free. Includes email support.

Serfler (New!)

A small web server written in Java "based almost entirely upon servlets". Property file driven. Available under the Gnu Public License.

WebEasy WEASEL Application Server

Contact for information.

Tandem's iTP WebServer

A web server with servlet support for those with Himalaya systems. Contact for pricing.

Novocode's NetForge

A web server written in Java. Free evaluation, free for non-commercial use. $80.

Enhydra

An open source Java application server. Sponsored by Lutris. They're in the process of migrating from the older Servlet API 1.0 to API 2.0. Free.

Locomotive

An open source Web application server. They support Servlet API 2.1 and are actively working on 2.2. Tested to work with several JSP engine plug-ins and on most major platforms. Also has hooks to plug-in to Apache and Netscape. Free (open source).

Orion Application Server (Updated!)

A pure-Java web server that is being written to support Servlet API 2.2 and JSP 1.1, along with EJB 1.1, JTA 1.0.1, JMS 1.0, JNDI 1.2, JDBC 2.0, RMI/IIOP, XML/XSL, and WAP. It's in beta. Will be a commercial product but free for non-commercial use.

An add-on servlet engine functions as a plug-in to an existing server--it adds servlet support to a server that was not originally designed with servlets in mind. Add-on servlet engines have been written for many servers including Apache, Netscape's FastTrack Server and Enterprise Server, Microsoft's Internet Information Server and Personal Web Server, O'Reilly's WebSite, Lotus Domino's Go Webserver, StarNine's WebSTAR, and Apple's AppleShareIP. This type of engine acts as a stopgap solution until a future server release incorporates servlet support. A plug-in also can be used with a server that provides a poor or outdated servlet implementation.

Java-Apache Project's JServ Module (Updated!)

A servlet engine that adds servlet support to the extremely popular Apache server. The 1.0 release supports Servlet API 2.0. In the long term future, this module will be replaced by Tomcat. Free, with source.

LiveSoftware's JRun Web Server

A plug-in designed to support the full Servlet API on all the popular web servers on all the popular operating systems! The latest version includes a simple web server for development purposes. JRun is free for development, testing, and non-commercial deployment and contains the full feature set of JRun Pro including JSP. JRun Pro is $595 for commercial deployment and features unlimited concurrency.

IBM's WebSphere Application Server (ServletExpress)

A plug-in that's part of an application server. It supports the full Servlet API on several popular web servers on several popular operating systems. Includes support for JSP. $795 Standard Edition, $6,000 Advanced Edition.

New Atlanta's ServletExec

A plug-in designed to support the full Servlet API on all the popular web servers on all the popular operating systems. Includes support for JSP. $395.

Unicom's Servlet CGI Development Kit

A framework that supports servlets on top of CGI What it lacks in efficiency it makes up for in ubiquity, and creativity. Free.

Gefion Software's WAICoolRunner (Updated!)

A plug-in that supports most of the Servlet API on Netscape's FastTrack Server and Enterprise Server versions 3.x, written in Java using Nescape's WAI interface. Free. The author Hans Bergsten reports that the plug-in does not work on iPlanet 4.0 "due to lack of WAI support in iPlanet 4.0 (it's no longer bundled and requires you to purchase the Inprise ORB, making a free servlet container add-on relying on it kind of a moot point)". This proves why you should be wary of building on vendor-specific technologies. What was free might start costing money.

An embeddable engine is generally a lightweight servlet deployment platform that can be embedded in another application. The application becomes the true server.

Acme Acme.Serve

Jef Poskanzer's simple web server that runs servlets "more of less compatible" with the Servlet API 1.0. Free.

Anders Kristensen's Nexus Web Server

A servlet runner that implements most of the Servlet API and can be easily embedded in Java applications. Free, but the server can be used only for non-commercial use.

Paralogic's Web Core Embeddable Server

A free but unsupported embeddable web server written in Java. It incorporates parts of Acme.Serve. Free.

Mort Bay's Jetty Server

An open source web server written in 100% Java designed to stand alone or be embedded (thus shown previously, above). Claims support for Servlet API 2.1; includes GNUJSP. No fee for use as it's distributed under the Open Source Artistic license.

A JSP embeddable engine provides support for JSP in a web server that already supports servlets.

GNUJSP (Updated!)

This popular open source JSP engine lets you run JSPs on almost any web server. The project was started by Vincent Partington, but after he gave up active development many others stepped in and as of October 1999 have released version 1.0. It supports JSP 1.0 on top of Servlet API 2.0 or 2.1. (Support on API 2.0 won't be complete as it's not possible.) Free under the GPL.

SJSP (Updated!)

Formerly known as Sator, this engine supports JSP 1.1 atop Servlet API 2.0 or later. You may wonder how that can work since JSP 1.0 and 1.1 depend on Servlet API 2.1. The answer is that SJSP on top of Servlet API 2.0 doesn't support JSP forward and include functionality. They also have a version that supports JSP 0.92 legacy code. Free for development, contact for commercial use. Commercial users get source.

zJSP

David Creemer's experimental JSP engine. Includes a program that converts .jsp files to .java servlets directly. David claims zJSP is intended just for him to play with JSP, but maybe you want to play too? Free.