Pencil Project

Pencil Project is an open-source desktop diagramming and GUI prototyping tool available for Linux, macOS, and Windows. Its collection of built-in interface stencils allows anyone to sketch software mockups directly on local storage without registering an account or paying recurring fees.

Why Pencil Project instead of Sketch

Commercial UI tools like Sketch charge recurring per-editor subscriptions and require Apple hardware. For non-technical professionals mapping out a form, dashboard layout, or screen sequence, ongoing seat licenses and dedicated Mac workstations introduce unnecessary expense. Pencil Project provides a local drafting canvas across Linux, Windows, and macOS at zero financial cost, storing document files on local disks without cloud lock-in.

The trade-off centers on production fidelity. Sketch excels at scalable vector illustration, nested symbols, auto-layout rules, and automated developer handoff plugins. Pencil Project does not attempt to match those production workflows; it focuses on low-fidelity wireframes and conceptual diagrams built from drag-and-drop primitives. For users who need clear interface mockups rather than production assets, Pencil Project eliminates the budget hurdles of commercial design platforms.

What it does well

• Pre-installed stencils: provides buttons, form inputs, tabs, and navigation bars for desktop and mobile layouts, removing the need to draw basic widgets by hand.
• Diagramming connectors: connects flowchart shapes with snapping lines that stay attached as shapes move, simplifying process flows and sitemaps.
• Multi-page document trees: organizes complex screens into hierarchical trees so teams can outline entire application workflows in one file.
• Inter-page hyperlinking: lets buttons and links jump between pages, creating clickable screen sequences for stakeholder walkthroughs.
• Diverse export formats: exports mockups to PNG, vector SVG, multi-page PDF, or HTML web pages without requiring recipients to run specialized tools.
• Offline storage: stores projects locally in zip-based files, keeping drafts private without network dependencies or third-party cloud hosting.

Limitations

• Linux startup stability: transitions to modern Electron runtimes can stall at startup, with issue reports like #820 documenting splash-screen freezes tied to renderer initialization and font handling.