OnUML

Web · API · paid plans from $8/mo

Freedom report

One barScore 5.2

Free tierA free tier is on its own pricing page
Open codeNo open-source code on record
Runs widely1 of 6 device platforms
DocumentedThinly documented

OnUML is ranked #25 of 32 in AI diagram generators on Freedom251. It runs on API, Web. There is a free plan. Paid plans start at $8/mo.

OnUML plans and pricing

All plans

Free Free forever 2 diagrams per project · 10 cloud projects per workspace · 2 workspaces · 10 free model requests per day · image upload not included onuml.com · 9 Oct 2026

Starter $4.90 once one-time 240 credits · credits expire 6 months after issue onuml.com · 9 Oct 2026

Pro $8/mo monthly; page also says “One-time payment” 500 monthly included credits · unlimited diagrams per project · unlimited cloud projects per workspace · unlimited workspaces · image upload included · no daily limit for free model requests onuml.com · 9 Oct 2026

Popular $9.90 once one-time 500 credits · credits expire 6 months after issue onuml.com · 9 Oct 2026

Pro Pack $19.90 once one-time 1,100 credits · credits expire 6 months after issue onuml.com · 9 Oct 2026

Compared on AI diagram generators

Free plan: Yes
Mermaid support: Yes
Platform: web
Export formats: PNG, SVG

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The record

Product: OnUML is an AI diagram generator and online UML editor for Mermaid, PlantUML, Draw.io, and mind maps.
Generation: It generates diagrams from natural-language prompts and supported image inputs.
Editing: Users can edit diagrams visually or through code and preview changes in real time.
AI repair: The editor offers one-click repair for Mermaid and PlantUML syntax errors.
History and organization: Users can save multiple code versions, restore earlier content, and organize diagrams by project.
Export and sharing: OnUML supports PNG and SVG export and shareable links.
Integrations: Its remote MCP server connects to coding agents including Codex, Claude Code, Cursor, and OpenClaw.
MCP access: The MCP server follows the signed-in account’s workspace permissions and supports reading and updating Mermaid, PlantUML, and OnUML mind maps; Draw.io is not supported through MCP.
MCP safeguards: OnUML says MCP updates check the latest diagram before changing it and stop if newer edits would be overwritten; retries are designed not to duplicate project or diagram creation.
Usage limits: The free plan allows 2 diagrams per project, 10 cloud projects per workspace, 2 workspaces, and 10 free model requests per day.
Credit limits: Purchased AI credits expire 6 months after issuance and do not unlock diagram, project, or workspace capacity.
Support: The site lists [email protected] as its contact email.
Operator: The site says OnUML is a product operated by myun L.L.C.
Price from: $8/mo

Where it ranks on Freedom251

Best AI Diagram Generators in 2026#25 of 32

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Sources

onuml.com· checked 9 Oct 2026
onuml.com/mcp-guide· checked 9 Oct 2026