kwasm

Standalone wasm-based client-only layout viewer for semiconductor designs, powered by KLayout.

kwasm compiles KLayout's layout rendering engine to WebAssembly via Emscripten, wrapped in a Rust FFI layer. The result is an interactive GDS2/OASIS viewer that runs entirely in the browser — no install required.

Features

• View GDS2 and OASIS layout files in the browser
• Pan, zoom, select, measure, and draw annotations
• Layer panel with per-layer visibility toggling and color display
• Toolbar with switchable interaction modes
• Dark and light theme
• Load layouts via drag & drop or ?url= query parameter
• Configurable toolbar via ?tools= query parameter
• Python package with embeddable Jupyter viewer
• CLI for bundling layouts into self-contained HTML files

Quick Start

# Build all WASM artifacts
just build

# Build docs site and serve at http://localhost:8080
just serve

Available Commands

Query Parameters

Available tool names for ?tools=:

Example: ?tools=ruler,top-ports,instance-ports shows only the ruler, top-level ports, and instance ports buttons.

Python Package

kwasm is available as a Python package that bundles the WASM viewer:

pip install kwasm

Jupyter Notebook

import kwasm

kwasm.show("my_chip.gds")
kwasm.show("my_chip.gds", lyp="layers.lyp", tools=("ruler", "fit-all"))

When used with gdsfactory, you can pass components directly:

import gdsfactory as gf
import kwasm

c = gf.components.mzi()
kwasm.show(c)

CLI

# Bundle a GDS into a self-contained HTML file
kwasm bundle my_chip.gds --output viewer.html --lyp layers.lyp

# Bundle and open in the default browser
kwasm view my_chip.gds

License

GPL-3.0

JavaScript Workspace (@gdsfactory/kwasm npm package)

The repo is an npm workspace; the publishable React library lives under packages/kwasm/ and the example Vite app under packages/example/.

Engines

• Node >=22.14
• npm >=11.5.1

Layout

packages/
  kwasm/         # @gdsfactory/kwasm — publishable Vite library
  example/       # Vite example app (private, not published)

Common commands

WASM artifacts

The packages/kwasm/wasm/ directory holds the modular ESM glue + gzipped WASM bytes consumed by the lib at consumer build time. It is populated by just build js-lib (added in Phase 1). The bundled-HTML pipeline (just build all) is unchanged.

Tooling

• TypeScript strict; target: ES2022, jsx: react-jsx; no paths aliases in packages/kwasm/src/ (would leak into emitted .d.ts).
• ESLint 10 flat config (typescript-eslint, react-hooks, jsx-a11y, eslint-config-prettier).
• Prettier 3.
• Pre-commit via prek (project convention — never pre-commit).
• Vitest 4 with unit (happy-dom) and browser (Playwright + Chromium) projects.

Supported consumer bundlers (v1)

Vite only. Next.js / Webpack / Rspack / esbuild are explicitly out of scope for v1 (locked in Phase 1 discussion, 2026-04-25). Other bundlers may work but are not validated in CI.