Mermaid Chart vs OpenCharts
Mermaid Chart
mermaid.aiOpenCharts
opencharts.comSide by side
| Figure | Mermaid Chart | OpenCharts |
|---|---|---|
| Price from | $12/mo | $9.99/mo |
| Free plan | Yes | Yes |
| Free trial | Yes | — |
| Open source | — | — |
| Web | Yes | Yes |
| Windows | — | Yes |
| macOS | — | Yes |
| API | Yes | Yes |
| Plans published | 4 | 4 |
| Spec score · AI Diagram Generators | 7.9 (#17) | 8.4 (#8) |
| Integrations | Official plugins and add-ons cover VS Code, JetBrains IDEs, Cursor, Windsurf, Claude Code, ChatGPT, Confluence, Jira, Google Docs, Microsoft Word, and PowerPoint. | Listed connectors include Stripe, HubSpot, Slack, Google Sheets, Discord, Airtable, Calendly, Apollo, Typeform, Monday, Gmail, Notion, GitHub, Linear, and others. |
| MCP server | Mermaid MCP can validate and render diagrams without authentication, while authenticated users can create, retrieve, update, and manage Mermaid Chart diagrams and projects. | Theo MCP provides 113 tools, five readable resources, a hosted Streamable HTTP endpoint, and 120 requests per minute per key. |
| Security | Mermaid states that it provides secure access controls, encryption, SOC 2 compliance, and SSO. | OpenCharts states that data is protected with TLS 1.2+ in transit, AES-256 at rest, SSO/SAML, RBAC, row-level security, and two-factor authentication. |
Plans
Mermaid Chart
- BasicFree
- Plus$12 a month
- Premium$24 a month
- EnterprisePriced on request
OpenCharts
- Free ForeverFree
- Starter$9.99 a month
- Pro$24.99 a month
- Teams$14.99 a month
In their own words
Mermaid Chart
Mermaid Chart turns plain-text Mermaid syntax into diagrams and refreshes the visual when the text changes. Mermaid AI can also create diagrams from natural-language prompts or uploaded PDF, Word and plain-text files. Supported types include flowcharts, sequence diagrams, Gantt charts, ER diagrams, timelines, mind maps, org charts, state and class diagrams, pie charts and quadrant charts. Teams can co-edit in real time, comment and share live links. Official plugins and add-ons connect it with development environments, AI assistants, documentation tools and office products, including VS Code, JetBrains IDEs, Cursor, Windsurf, Claude Code, ChatGPT, Confluence, Jira, Google Docs, Word and PowerPoint. Mermaid AI exports PNG and SVG files. Mermaid MCP can validate and render diagrams without authentication; authenticated users can use it to manage diagrams and projects. Basic costs nothing and includes three diagrams and 15 AI credits. Plus costs $12 a month billed annually; Premium costs $24 a month billed annually. Trial and paid-tier content is not used to train Mermaid AI models; Basic-tier content may be used to improve services.
OpenCharts
OpenCharts is an AI workspace for flowcharts, presentations, notes, code, video, and agents. Theo AI can create these materials from plain-language descriptions. Flowcharts use terminal, process, decision, and data nodes on an infinite canvas, with automatic layout and export tools. The presentation editor supports editable slides, speaker notes, transitions, AI generation, rehearsal coaching, web publishing, and PPTX export. Theo Agents can start on schedules, webhooks, monitoring triggers, or manually; they can use external connectors, human approval gates, and produce deliverables. Connectors include Stripe, HubSpot, Slack, Google Sheets, Discord, Notion, GitHub, and others. A REST API manages project types, and the Theo MCP server provides 113 tools and five readable resources. Each account starts with 10 GB of Drive storage, including Free Forever. That plan costs nothing and includes 500K AI credits and one of each project type. Starter costs $9.99 a month, Pro $24.99 a month, and Teams $14.99 a month with a three-user minimum. OpenCharts says it does not use customer data to train or fine-tune AI models.