Text to diagram. Unlimited AI, on your device.

Diagram Studio is a free AI diagram generator that runs entirely in your browser. Describe what you want — a signup flow, a database schema, a sprint board, a release timeline, a C4 deployment view — and a small on-device language model writes the Mermaid code, renders it live while it streams, and lets you regenerate, refine and restyle it before exporting as SVG or PNG. There is no server-side generation, so generations are unlimited on every plan, including free.

It is built for the situations where cloud diagram tools are the wrong answer: turning a meeting note into a sequence diagram in seconds, drafting a private ER schema for a client system you cannot put on someone else's server, or producing a publishable flowchart without an account. Eighteen diagram types, six themes, three visual looks, AI variations and one-click refine, 19 starter templates, a local library, self-contained share links and watermark-free exports are all built in. Nothing you write leaves your device.

How on-device AI generation works

Two engines sit behind the same interface. The first is Chrome's built-in AI (the LanguageModel API, available in Chrome 127+ and other Chromium browsers that ship Gemini Nano). It runs the model the browser already has embedded, so there is nothing to download and generation starts immediately. The second engine is a local Qwen2.5 1.5B-Instruct model loaded through Transformers.js on WebGPU, with a WebAssembly fallback when WebGPU is unavailable — a one-time download of roughly 1 GB, cached by the browser for offline use afterwards.

Whichever engine runs, the output is a Mermaid code block. A regex-based auto-fixer repairs the common slips a 1.5B model makes — unbalanced subgraph ends, missing diagram-type keywords, unclosed quotes in node labels — before the code reaches the renderer. Mermaid 11 then parses and renders it: a streaming-tolerant mode silently ignores mid-generation syntax errors so the canvas updates token by token, and a final render surfaces real errors with a clear message you can fix in the code editor.

Eighteen diagram types, or Auto

Eighteen Mermaid-powered diagram types are supported: flowchart, mindmap, sequence, class, state, entity-relationship, Gantt, git graph and pie cover the classic software and project cases; timeline and user journey map explain what happens over time; kanban and quadrant chart organize work and trade-offs; C4 diagrams describe system context, containers and deployment; radar and XY charts visualize scored and numeric data; Venn diagrams show overlap; and the Ishikawa (fishbone) diagram structures root-cause analysis. A few of the newest types use Mermaid's beta syntax and are labelled as such — they render reliably but occasionally need a small manual touch.

You can pin a type explicitly, or leave the selector on Auto and let the model pick the representation that fits your prompt — database tables tend to become an ER diagram, message exchange a sequence diagram, a sprint board a kanban. The same prompt can also be explored as multiple AI variations, each generated at a different temperature, so you can compare a conservative layout against more creative ones.

Themes, looks and direction

Six themes recolour any diagram instantly without re-running the model: Graphite (the default cool-grey palette), Cobalt (a single-accent blue scheme), plus Mermaid's Default, Neutral, Dark and Forest. Three looks change the visual register: Neo is the clean modern style, Classic is the traditional Mermaid look, and Hand-drawn renders sketchy, Excalidraw-style strokes for whiteboard brainstorms.

Direction switches flowcharts and other directional diagrams between top-down (TD) and left-right (LR); the flip-direction refine action can also regenerate the layout rather than merely rotating it. Because the code itself is theme-, look- and direction-agnostic, restyling never destroys your edits.

AI variations and refine actions

Every generation can produce one, two or four variations. The free plan generates one variation per run — with no limit on the number of runs — while Pro unlocks two and four, generated serially at rising temperatures (0.2, 0.5, 0.75 and 0.95) so the set spans safe to creative. Switch between V1–V4 instantly; hand-editing the Mermaid code of one variant never overwrites the others.

Six refine actions operate on the current diagram without starting over: Fix repairs syntax, Simplify removes redundant nodes and edges, Add detail enriches a sparse draft, Beautify cleans up wording and grouping, Flip direction regenerates in the opposite orientation, and Custom applies an instruction you type in your own words. Each refine is a fresh on-device generation, so it stays unlimited too.

Templates, saved library and history

Nineteen built-in templates cover every diagram type with realistic, searchable starting points — open the template browser, filter by name, load one and edit the Mermaid directly. Templates make the specialized diagrams (C4, fishbone, kanban, journey map) usable even without knowing their syntax.

A Save button stores the current diagram with a name in your browser: the free plan keeps up to 12 saved diagrams and Pro up to 200. Separately, the last 20 generations on free (100 on Pro) are kept automatically in Recent, each with its prompt, type and timestamp, and any entry can be reloaded or deleted. Everything lives in localStorage on your device — there is no cloud library, no account sync and nothing that can leak. Free prompts run up to 2,000 characters; Pro raises that to 12,000.

Sharing without a server

Share does not upload anything. The current diagram code, type, theme, look and direction are compressed with deflate-raw and encoded into a self-contained URL hash. Anyone opening the link restores the exact diagram on their own device; there is no database record and nothing to delete server-side. Because the data sits after the #, it never reaches a web server at all. Once the diagram is restored, the hash is cleared from the address bar, so reloading or bookmarking the page will not reopen the shared draft.

Canvas controls and export

The canvas supports wheel and trackpad zoom anchored at the cursor, drag-to-pan, double-click to fit, a fullscreen mode (enter and exit with Esc), and live re-rendering on every code edit. The Mermaid code stays exposed in an editor next to the canvas, so the editor — not a read-only artifact — is always the source of truth.

Exports are generated client-side from the rendered SVG: downloadable SVG (vector, infinite resolution) and PNG at 2× and 4× on the free plan, with 8× unlocked on Pro, plus one-click Copy SVG and Copy PNG. There is no server round-trip, no watermark and no account, on either plan.

Limits, requirements and privacy

The local Qwen model needs a reasonably modern device — WebGPU matters for speed, and 1.5B parameters still means multi-second generation for a complex diagram. Chrome's built-in AI path is faster and download-free but only exists on Chromium browsers shipping Gemini Nano. If neither engine is available, the tool remains a full Mermaid editor: write code by hand, get live rendering, templates, themes and the same export options. A 1.5B model is not a frontier model — treat its output as a first draft and expect occasional manual fixes, especially for the beta diagram types and strict UML semantics.

Because generation costs the service nothing, there is no daily or monthly generation cap on either plan: the free limits are 1 variation per run, 12 saved diagrams, 20 recent items, 2,000-character prompts and 4× PNG; Pro adds 4 variations, 200 saved diagrams, 100 recent items, 12,000-character prompts and 8× PNG. Your prompt and Mermaid code never leave the browser, there is no logging or prompt analytics, and the only network request the tool ever makes is the one-time model download from a public CDN — after which it works offline.