kitio.aiMermaid Viewer vs OnUML
A side-by-side look at pricing plans, free tiers, features, pros and cons, updated for 2026. Mermaid Viewer starts at See pricing page and OnUML starts at See pricing page. Check both pricing pages for current plans.
At a glance
Best for
Pricing model
Starting price
Free plan
Made by
Based in
Rating
Key features
- Live Mermaid preview
- Text-to-diagram AI
- Syntax error fixes
- SVG, PNG and PDF export
- Shared editing links
- Docker self-hosting
- Text or image to diagram
- Mermaid and PlantUML editors
- Draw.io canvas mode
- Editable mind maps
- AI code repair
- MCP server
| Feature | Mermaid Viewer | OnUML |
|---|---|---|
| Best for | Browser editor for Mermaid diagrams with AI code generation | AI diagram maker for Mermaid, PlantUML, Draw.io and mind maps |
| Category | Design | Design |
| Pricing model | Freemium | Freemium |
| Starting price | See pricing page | See pricing page |
| Free plan | Yes | Yes |
| Made by | Mermaid Viewer | OnUML |
| Based in | – | – |
| Rating | No ratings yet | No ratings yet |
| Key features |
|
|
Pricing compared
Mermaid Viewer starts at See pricing page and OnUML starts at See pricing page. Check both pricing pages for current plans.
Free plan
Cheapest paid plan
Top plan
Free trial
3 plans
Free
Free
- 3 diagrams
- 5 AI conversations per day
- Watermarked low-res PNG
Starter
$69.99/yr billed yearly
- 30 diagrams
- 500 AI conversations per month
- High-res PNG without watermark
- 30 saved versions
Pro
$119.99/yr billed yearly
- Unlimited diagrams
- Unlimited AI conversations
- PNG, JPG, PDF and SVG export
- 100 saved versions
Prices in USD, checked Nov 5, 2026 or later. Plans change often, so confirm on each tool's site before you buy.
Pros and cons
Mermaid Viewer
- No install, runs in the browser
- AI drafts diagram code from text
- Many export formats on paid plans
- Free plan allows only 3 diagrams
- Free exports are low-res and watermarked
- Monthly prices not shown, only yearly
OnUML
- Four diagram formats in one place
- Fixes broken diagram code
- Free daily credits
- Pricing hidden behind sign-in
- Daily free credits are small
- Formal UML still needs some know-how
Which one should you choose?
Choose Mermaid Viewer if you want:
- No install, runs in the browser
- AI drafts diagram code from text
- Many export formats on paid plans
Watch out: free plan allows only 3 diagrams.
Choose OnUML if you want:
- Four diagram formats in one place
- Fixes broken diagram code
- Free daily credits
Watch out: pricing hidden behind sign-in.
Mermaid Viewer vs OnUML FAQ
What is the difference between Mermaid Viewer and OnUML?
Mermaid Viewer: Browser editor for Mermaid diagrams with AI code generation. OnUML: AI diagram maker for Mermaid, PlantUML, Draw.io and mind maps. Both are design tools.
Is Mermaid Viewer or OnUML cheaper?
Mermaid Viewer starts at See pricing page and OnUML starts at See pricing page. Check both pricing pages for current plans.
Do Mermaid Viewer and OnUML have free plans?
Mermaid Viewer: Yes. OnUML: Yes.
Who makes Mermaid Viewer?
Mermaid Viewer is made by Mermaid Viewer.
Who makes OnUML?
OnUML is made by OnUML.
Which should I choose, Mermaid Viewer or OnUML?
Choose Mermaid Viewer if you value no install, runs in the browser and ai drafts diagram code from text. Choose OnUML if you value four diagram formats in one place and fixes broken diagram code.