Mermaid Chart

✓ Verified

★★★★★

(4.3) $10/month Freemium ✓ Free Trial Available

Web API Extension

Diagram as code platform with an AI editor that writes and fixes Mermaid diagrams from prompts.

Best For: Developers and technical writers who keep diagrams as code in docs and repos

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The Verdict: Mermaid Chart

Mermaid Chart is the developer pick in this category: AI written diagram code that lives in your repos and docs, with an editor that fixes syntax as well as generating it. The yearly credit pool and the code first interface narrow its audience. Teams that document software for a living will find it the most maintainable option here.

What is Mermaid Chart?

Mermaid Chart is the hosted platform for Mermaid, the diagram as code syntax that developers already embed in GitHub readmes, wikis and documentation. Its AI chat writes Mermaid code from a plain language description and, just as usefully, repairs broken or messy code you paste in. The output covers flowcharts, sequence diagrams, class and state diagrams, ER diagrams, Gantt charts, user journeys, git graphs, mind maps and timelines.

Because diagrams are stored as text, they version in Git, diff cleanly in pull requests and never lock a team into a binary file format. A visual editor sits beside the code for layout adjustments, and VS Code and IDE extensions in the wider Mermaid ecosystem keep the same diagrams editable inside the tools developers already use.

The pricing model needs one warning. Paid plans are billed per user annually, and AI credits come as a yearly pool rather than a monthly allowance, so a heavy documentation sprint can consume a noticeable share early. The free Basic plan limits diagram count and size. For documentation heavy engineering teams, that trade is usually worth it; for canvas first users, it is not the right shape at all.

Who is Mermaid Chart Best For?

Developers and technical writers who keep diagrams as code in docs and repos

Mermaid Chart Key Features

AI chat that writes Mermaid diagram code from plain language prompts

AI fixes and edits to existing diagram code

Flowcharts, sequence diagrams and class diagrams in Mermaid syntax

State diagrams, ER diagrams and Gantt charts

User journey, git graph, pie chart and timeline diagrams

Mind maps in Mermaid syntax

Visual editor alongside the code for layout adjustments

Version friendly text format that fits Git workflows

VS Code and IDE extensions in the Mermaid ecosystem

Team and project workspaces on paid plans

Unlimited free viewer seats on the Premium plan

AI credits allocated per year on paid plans

Mermaid Chart Pricing & Plans

Mermaid Chart Review Summary

Performance Score	B
Content Quality	Accurate, syntax correct diagrams that render consistently anywhere Mermaid is supported.
Interface	A code first editor with a visual side, best for users comfortable with text.
AI Technology	Prompt based code writing and repair, metered by yearly AI credits.
Purpose	Creating and maintaining diagrams as code for software documentation.
Compatibility	Web, API, Extension
Pricing Summary	Mermaid Chart starts at $10/month per user on annual billing after a free Basic plan with limited diagrams.

Mermaid Chart Pros & Cons

✅ Pros

Diagrams live as text, so they version, diff and review like code
The AI editor fixes broken syntax instead of only generating new diagrams
Every Mermaid diagram type is supported, from ER to git graphs
Viewer seats are free on Premium, which suits documentation teams
The free plan is enough to learn the Mermaid workflow properly

❌ Cons

AI credits are counted per year, so heavy months eat a visible share
There is a learning curve if you have never touched diagram code
The free plan caps diagram size and count
Canvas style freehand editing is limited compared to whiteboard tools

FAQs

Is Mermaid Chart free to use?

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Yes. The free Basic plan covers a limited number of diagrams with a size cap and limited AI use, which is enough to learn the workflow before paying.

How does Mermaid Chart pricing work?

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Paid plans are billed per user on annual billing, and AI credits are allocated per year rather than per month. The starting figure is in the pricing summary below.

What is Mermaid diagram code?

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Mermaid is a text syntax that renders as diagrams. You describe nodes and connections in plain text, and the tool draws the flowchart, sequence diagram or ER diagram from that text.

How many AI credits do the plans include?

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Entry paid plans include a few hundred AI credits per year and the higher tier includes a few thousand, so heavy generation months should be planned against the yearly pool.

Which diagram types does Mermaid Chart support?

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Everything Mermaid syntax supports: flowcharts, sequence diagrams, class diagrams, state diagrams, ER diagrams, Gantt charts, user journeys, git graphs, pie charts, mind maps and timelines.