# Best open source apps written in Java > The best self-hosted apps written in Java are ElasticSearch, Keycloak and Halo. ElasticSearch leads with 78,194 GitHub stars. Candidates: the 50 apps whose main GitHub language is Java. ## Key facts | Fact | Value | |---|---| | Question | What are the best self-hosted apps written in Java? | | Picks | 12 | | Top pick | ElasticSearch (78,194 stars) | | Data as of | Oct 7, 2026 | | Canonical URL | https://appsgit.com/best/open-source-apps-in-java | ## Ranked picks - [ElasticSearch](https://appsgit.com/apps/elasticsearch) (78,194 stars, AGPL-3.0 / SSPL-1.0 / Elastic-2.0, Java): ElasticSearch has 78,194 GitHub stars, uses the AGPL-3.0, SSPL 1.0 or Elastic License 2.0 (your choice) license, is written in Java and had 13,336 commits in the last year; it replaces Algolia. - [Keycloak](https://appsgit.com/apps/keycloak) (37,156 stars, Apache-2.0, Java, Docker): Keycloak has 37,156 GitHub stars, uses the Apache-2.0 license, ships a Docker image, is written in Java and had 3,157 commits in the last year; it replaces Auth0 and Okta. - [Halo](https://appsgit.com/apps/halo) (39,927 stars, GPL-3.0, Java, Docker): Halo has 39,927 GitHub stars, uses the GPL-3.0 license, ships a Docker image, is written in Java and had 580 commits in the last year. - [Kestra](https://appsgit.com/apps/kestra) (29,274 stars, Apache-2.0, Java, Docker): Kestra has 29,274 GitHub stars, uses the Apache-2.0 license, ships a Docker image, is written in Java and had 4,392 commits in the last year; it replaces Zapier. - [Jenkins](https://appsgit.com/apps/jenkins) (26,618 stars, MIT, Java, Docker): Jenkins has 26,618 GitHub stars, uses the MIT license, ships a Docker image, is written in Java and had 1,159 commits in the last year; it replaces GitHub Actions / CircleCI. - [Mindustry](https://appsgit.com/apps/mindustry) (29,232 stars, GPL-3.0, Java): Mindustry has 29,232 GitHub stars, uses the GPL-3.0 license, is written in Java and had 1,920 commits in the last year. - [Apache SkyWalking](https://appsgit.com/apps/apache-skywalking) (24,967 stars, Apache-2.0, Java, Docker): Apache SkyWalking has 24,967 GitHub stars, uses the Apache-2.0 license, ships a Docker image, is written in Java and had 265 commits in the last year. - [LanguageTool](https://appsgit.com/apps/languagetool) (15,107 stars, LGPL-2.1, Java, Docker): LanguageTool has 15,107 GitHub stars, uses the LGPL-2.1 license, ships a Docker image, is written in Java and had 1,930 commits in the last year. - [Druid](https://appsgit.com/apps/druid) (14,059 stars, Apache-2.0, Java, Docker): Druid has 14,059 GitHub stars, uses the Apache-2.0 license, ships a Docker image, is written in Java and had 1,223 commits in the last year. - [OpenSearch](https://appsgit.com/apps/opensearch) (13,815 stars, Apache-2.0, Java, Docker): OpenSearch has 13,815 GitHub stars, uses the Apache-2.0 license, ships a Docker image, is written in Java and had 1,370 commits in the last year; it replaces Algolia. - [OneDev](https://appsgit.com/apps/onedev) (15,281 stars, MIT, Java, Docker, AI features): OneDev has 15,281 GitHub stars, uses the MIT license, ships a Docker image, is written in Java and had 608 commits in the last year; it replaces GitHub and GitLab. - [Thingsboard](https://appsgit.com/apps/thingsboard) (22,512 stars, BUSL-1.1, source-available, Java, Docker): Thingsboard has 22,512 GitHub stars, is source-available under the BSL 1.1 (not an open-source license), ships a Docker image, is written in Java and had 3,539 commits in the last year. ## How this list was made - Candidates: the 50 apps whose main GitHub language is Java. - Base score: GitHub stars on a log scale plus commits in the last 12 months (log scale, capped at 1,000). - Bonus points for a published Docker image, an OSI-approved open-source license and a commit in the last 90 days. - The language is GitHub's detection for the repository; many projects also use other languages. ## FAQ ### Is ElasticSearch free? Yes. ElasticSearch is open-source software released under the AGPL-3.0, SSPL 1.0 or Elastic License 2.0 (your choice) license, so you can self-host it at no cost. You only pay for the server it runs on, and some projects also offer an optional paid cloud plan. ### Can I self-host these apps with Docker? Yes, 10 of the 12 picks. Keycloak, Halo and Kestra publish Docker images, so you can run them on a VPS or home server with Docker Compose. The others install from their own packages or source; follow each project's install guide. ### Are all of these apps open source? 11 of the 12 apps on this list are open source; 1 is source-available. Source-available licenses add conditions, such as limits on hosted or commercial use, so read them before you deploy. ### Which of these apps is the most actively developed? ElasticSearch, with 13,336 commits in the last 12 months and a latest release, v9.5.4, from September 2026. Activity is a good sign that bugs and security issues get fixed. ## Related questions - [What are the best self-hosted apps written in C#?](https://appsgit.com/best/open-source-apps-in-c-sharp) - [What are the best self-hosted apps written in Ruby?](https://appsgit.com/best/open-source-apps-in-ruby) - [What are the best MIT-licensed self-hosted apps?](https://appsgit.com/best/mit-licensed-self-hosted-apps) - [What are the best AGPL-licensed self-hosted apps?](https://appsgit.com/best/agpl-self-hosted-apps) - [What are the best self-hosted apps for beginners?](https://appsgit.com/best/docker-self-hosted-apps-for-beginners) - [What are the best source-available self-hosted apps?](https://appsgit.com/best/source-available-apps) - [What are the trending GitHub projects right now?](https://appsgit.com/best/trending-github-projects) - [What is the best open source PDF editor you can self-host?](https://appsgit.com/best/open-source-pdf-tools) ## See also - [Open-source alternatives to Algolia](https://appsgit.com/alternatives/algolia) - [Open-source alternatives to Auth0](https://appsgit.com/alternatives/auth0) - [Open-source alternatives to Okta](https://appsgit.com/alternatives/okta) - [Open-source alternatives to Zapier](https://appsgit.com/alternatives/zapier) - [Open-source alternatives to GitHub Actions / CircleCI](https://appsgit.com/alternatives/github-actions) - [Open-source alternatives to GitHub](https://appsgit.com/alternatives/github) - [Keycloak vs authentik](https://appsgit.com/compare/keycloak-vs-authentik) --- Canonical page: https://appsgit.com/best/open-source-apps-in-java Source: appsgit (https://appsgit.com), the app store for github. 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