From source to export plan
Open the split workspace at /app/?lang=en&tool=flowchart, paste Mermaid source into the left pane (for example the four-node sample starting with flowchart LR), and press Run.
The validate phase does type detection, the 100KiB / 1000-node budget, strict security filtering and per-line structural validation; every error returns line N, column M (node X) and preserves your input. The render phase builds a deterministic SVG inside a module Worker; the export phase assembles the SVG and PNG export plans.
The result pane shows copyable/downloadable SVG text, a safe preview and metadata. The export plan records the local worker path, a system font stack, zero network requests, the PNG non-blank-canvas policy and a cancellable 8-second timeout. Deep links also work under the /sandbox/diagram/ subpath.
Replace flowchart with sequenceDiagram, classDiagram or gantt on the matching operation page to get recognizable participant/message, class/relation, and section/task structures.