Top Open Source Projects Built With Java in 2026
A curated collection of the 40 best free and open-source projects built using Java. Discover popular repositories, architecture patterns, and trending software in 2026.
xyd
Open source framework for building beautiful docs
Stars113Last commit12d agoLicenseMIT
XWiki
Open source enterprise wiki and knowledge base
Stars1,302Last commit10d agoLicenseLGPL-2.1SeriesGuide
Android app for tracking TV shows and movies you're watching, have watched, or plan to watch, powered by TMDb data.
Stars2,147Last commit17d agoLicenseOpen SourceLibreOffice
Free and private office suite, no forced AI
Stars4,278Last commit10d agoLicenseGPL-3.0Keycloak
Open source identity and access management
Stars36,444Last commit10d agoLicenseApache-2.0
Gravitee
AI Agent Management platform for enterprise scale
Stars445Last commit10d agoLicenseApache-2.0Firecrawl
API for AI agents to search, scrape, crawl, and interact with the live web, returning clean Markdown, structured JSON, or screenshots from any page.
Stars173,014Last commit10d agoLicenseAGPL-3.0draw.io
Free open-source diagramming tool for teams
Stars7,753Last commit15d agoLicenseApache-2.0ByteChef
Open-source workflow & AI agent builder
Stars992Last commit10d agoLicenseOpen SourceAutoMQ
Diskless Kafka on S3 with sub-10ms latency
Stars10,576Last commit11d agoLicenseApache-2.0SuperTokens
Open source user authentication for apps
Stars15,285Last commit16d agoLicenseOpen Source
Structr
Open-source low-code platform with built-in graph database
Stars828Last commit27d agoLicenseOpen Source
Standard Notes
End-to-end encrypted notes app with unmatched privacy
Stars6,604Last commit12d agoLicenseAGPL-3.0
Signal
Privacy-first encrypted messaging app
Stars29,260Last commit11d agoLicenseAGPL-3.0
Scalar
Open-source API documentation & SDK platform
Stars16,004Last commit10d agoLicenseMIT
