Real shapes, not dropped pixels
Every shape carries meaning — service nodes, queues, databases, network boundaries. Vellum understands what you're drawing so the diagram can be linked, navigated, and annotated, not just rendered.
Vellum · Editor
A diagram editor built for the explanation, not the drawing.
Vellum is the open diagram editor that ships with Blueprintr — built for system designs, software architectures, infrastructure topologies, and process flows. Real shapes, real exports, no lock-in.
Strata for layered explanations
Click a shape to drill into a Stratum — a focused panel of prose, code, or sub-diagrams that explains the part. The top-level picture stays clean; the depth lives where the reader asks for it.
No lock-in
Open-source editor (JGraph & Apache-2.0 stack), self-hostable bundle, exportable to SVG / PNG / embeddable HTML. Your diagrams are yours, in formats you can read without us.
Built for diagram-first documentation that never drifts
Vellum is the editor that powers diagrams on Blueprintr. Every published blueprint starts with the picture — Vellum is what authors use to draw it. The same bundle ships at vellum.blueprintr.io for standalone use, and the editor's icon packs, shape libraries, and saving model are open and self-hostable.
If you're choosing between drawio, Excalidraw, Mermaid, and Vellum — the answer's that they each have a place. drawio is unmatched for traditional flowcharts; Excalidraw owns whiteboard sketches; Mermaid is the right call for text-driven sequence and class diagrams. Vellum is for the in-between case: real shapes (drawio's strength), modern UX (Excalidraw's strength), but built explicitly to be the centre of an explanation, not an attachment to one.
See it in a published blueprint
The fastest way to grok Vellum is to read a Blueprint that uses it. See a live blueprint on the homepage — it renders its diagram inline with a Vellum or drawio canvas, and Strata panels open over the diagram for the deep dive.