Side by side
OnUML vs OpenFlowKit
Both stand on ai diagram generators. Which one you can start free with, which one lets you read the code, and what each costs once you pay.
OnUML offers diagram generation, editing, version recovery, and sharing, with MCP access for several coding agents. Review the free-plan capacity and credit expiry, and note that the Pro billing description is inconsistent about whether payment is monthly or one-time.
Visit OnUML
Choose OpenFlowKit if you want a free diagram tool that combines code imports, visual editing, and local-first storage. Its MIT-licensed core and broad export options also suit builders who want to host or modify the engine. Look elsewhere if you need AI generation without supplying your own provider key.
Visit OpenFlowKitThe facts
| OnUML | OpenFlowKit | |
|---|---|---|
| Free plan | Yes | Yes |
| Open source | Not published | Not published |
| Runs on | API, Web | Web |
| Lowest paid plan | See the plans | Free or on request |
| Plans published | 5 | 1 |
| Maker | Not published | Not published |
| Website | onuml.com | openflowkit.com |
| On ai diagram generators | #24 of 32 | #28 of 32 |
OnUML: what it does well
- Generates diagrams from prompts and supported image inputs.
- Supports visual and code editing with live preview.
- Can repair Mermaid and PlantUML syntax errors.
- Exports PNG and SVG and offers shareable links.
- MCP checks for newer edits before updating diagrams.
What to know first
- Free plan allows only two diagrams per project.
- Free plan excludes image uploads.
- Draw.io is not supported through MCP.
- Purchased AI credits expire six months after issuance.
OpenFlowKit: what it does well
- Parses JSON, React components, Prisma schemas, and SQL dumps into diagrams.
- Supports a type-safe DSL and Mermaid.js for diagram definitions.
- Offers peer-to-peer collaboration with live cursors.
- Exports diagrams to PNG, JPG, SVG, JSON, Mermaid, PlantUML, WebM, and MP4.
- The core engine is MIT licensed and can be hosted or modified freely.
What to know first
- AI generation requires the user's own OpenAI or Anthropic key.
- The project describes itself as just getting started.
Alternatives to OnUML Alternatives to OpenFlowKit The whole list