Google Sheets ported its calculation worker from JavaScript to WasmGC

Original Article ↗ Hacker News Discussion ↗

Performance and results

  • Initial WasmGC port of the Sheets calculation engine ran about 2× slower than the existing JS-targeted version.
  • After substantial optimization (devirtualization, speculative inlining, better data structures, and using native browser APIs like RegExp), the WasmGC version is about 4× faster than that prototype and roughly 2× faster than the JS version.
  • Java-on-WasmGC is said to be ~2× slower than Java on the JVM, so there is still a gap to native JVM performance.

Java, JavaScript, and what’s actually being compared

  • The engine is written in Java and compiled either to JS (via J2CL/GWT) or to WasmGC (via J2Wasm).
  • Some argue the article blurs the distinction by talking about “JavaScript vs Java,” when it is really comparing compilation targets for the same Java code.
  • Others counter that the “JS version” is a real JS bundle delivered to the browser and historically replaced a handwritten JS implementation, so comparing “JS vs WasmGC” is fair from a web-performance perspective.

Why WasmGC matters

  • Without WasmGC, GC’d languages must ship their own collectors in Wasm, inflating binary size and complicating cross-module and host integration.
  • WasmGC lets languages reuse the browser’s GC, improves interop (e.g., sharing heap objects across modules/host), and avoids tricky “hybrid” GC schemes.
  • Limitations remain: GC arrays lack some low-level ops (e.g., efficient reinterpretation of bytes as ints), and sharing packed GC arrays efficiently with WebGL/WebGPU/Web Audio is still awkward.

Browser support and fallbacks

  • Chromium-based browsers and Firefox support WasmGC; Safari/WebKit work is ongoing but incomplete.
  • Sheets can still serve a JS-compiled version where WasmGC is unavailable.

Comparisons to Excel and scalability

  • Native Excel (C++) is expected to remain faster, with no 4 GB Wasm memory cap and real shared-memory threads.
  • Users report Sheets becoming slow or hanging with large, complex models, while Excel handles similar workloads better; others mainly notice UI sluggishness, not raw calculation speed.

Offline, native, and platform lock-in

  • Some want a true offline/standalone Sheets app; today’s offline mode requires Chrome/Edge and an extension.
  • This raises complaints about browser lock-in and potential antitrust concerns; others note limited incentive to support more browsers.

Meta: publication dates and credibility

  • Several comments criticize the article’s lack of a clear original publication date and describe a broader trend of hiding dates for SEO/engagement, which they see as harmful to trust and technical context.