Apache Tomcat
open-source
Open-source Java servlet container and web server for deploying Java-based web applications.
Open source application server software to evaluate in 2026
Open source application server software gives teams full code access, no per-user licensing, and the freedom to self-host, but operational cost replaces license cost. These are the open source options in this category, followed by the full list for comparison.
6 of 8 products in this category match the open source filter and are highlighted below.
Back to all Application Server Software tools, or browse the full software directory. You can also run head-to-head comparisons or read about our review methodology.
For background on scoring, see how rankings work. Our editorial articles add deeper analysis, the glossary clarifies vendor terminology, and our calculators help estimate ROI before the shortlist narrows further.
Open source options
GlassFish
open-source
Open-source Jakarta EE-compliant application server for enterprise Java workloads.
Gunicorn
open-source
Python WSGI HTTP server for running Django and Flask applications in production.
Puma
open-source
Concurrent Ruby HTTP server designed for speed and parallelism in Rails and Rack applications.
Uvicorn
open-source
Lightning-fast ASGI server for Python async frameworks like FastAPI and Starlette.
WildFly
open-source
Open-source Jakarta EE application server, the community upstream of Red Hat JBoss EAP.
Other application server software
The rest of the application server software category, listed because the open source filter above did not select them. Worth reading when the highlighted options do not fit.
Microsoft IIS
subscription
Windows-native web server for hosting ASP.NET, PHP, and static sites with deep Windows Server integration.
Nginx
freemium
High-performance web server, reverse proxy, and load balancer with a commercial Plus tier.
Common questions about open source application server software
Is open source application server software really free?
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The license is free, but hosting, maintenance, patching, and upgrades replace the vendor's license fee. Teams without dedicated ops resources often spend more on self-managed open source than on a managed commercial alternative.
When should I choose open source over commercial application server software?
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Open source is strongest when you need full code control, on-premises deployment for compliance, or want to avoid vendor lock-in. It is weaker when your team lacks the ops capacity to maintain, patch, and scale the deployment.
What should I check before deploying open source application server software?
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Check community activity (commits, issues, and releases in the last six months), commercial support options, documentation quality, and the total operational burden against a managed alternative. A dormant project with no commercial backing is a risk.