Fess vs Onyx
Fess
fess.codelibs.orgOnyx
onyx.appSide by side
| Figure | Fess | Onyx |
|---|---|---|
| Price from | Free | $20/mo |
| Free plan | Yes | Yes |
| Free trial | — | Yes |
| Open source | — | Yes |
| Web | Yes | Yes |
| Windows | Yes | Yes |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| API | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 2 | 3 |
| Spec score · AI Enterprise Search Software | 8.3 (#6) | 8.9 (#3) |
| API | Fess documentation covers an API, and external system integration can use access tokens. | Nearly every feature is exposed through a REST API using JSON, with Bearer API keys or personal access tokens and an OpenAPI explorer at /api/docs. |
| Deployment | Fess runs on operating systems with a Java or Docker runtime environment. | Onyx can run as self-hosted Standard or Lite, in Docker Compose, Kubernetes/Helm or cloud infrastructure, and is also offered as managed Onyx Cloud. |
| Integrations | Fess can return search results in JSON, integrate with websites using JavaScript, and extend functionality through plugins. | The product advertises more than 50 synced connectors and names Slack, Google Drive, Confluence, Salesforce, GitHub and Jira among supported sources. |
| Support | The open-source edition is community-supported and has no guaranteed support; paid professional support is available by email. | The Business plan includes Community Support; Enterprise lists Dedicated Support and an Enterprise SLA. |
Plans
In their own words
Onyx
Onyx connects enterprise knowledge so people and AI agents can use relevant context in answers. It searches indexed sources in parallel and presents documents while enforcing each source's permissions. More than 50 connectors sync connected tools in the background and support hybrid semantic and keyword search. The Business plan lists chat and search, major LLM access, custom agents, MCP/OpenAPI actions, web search, deep research, code interpreter, and image generation. Business costs $20 a month, billed annually at $20 per user per month, for teams of any size, with 40+ app connectors and Community Support. Onyx provides APIs for messages, agents, LLM management, actions, and user authentication. Slack integrations can provide responses and agents; Microsoft Teams and Zendesk are described as coming soon. Deployments can run in a customer's cloud or on bare metal, including on-premise and fully air-gapped environments. The site says documents and embeddings can remain in customer infrastructure, data is not used for training, and permissions are checked at query time. Native Windows, macOS, and Linux apps connect to an existing deployment.