Cloudflare Workers

Since vellora 0.4.0.

Workers can't load a native Node addon, so vellora ships its engine a second way: compiled to WebAssembly, as @vellora/wasm. Your code doesn't change. On workerd, vellora picks the WebAssembly engine by itself.

npm install vellora @vellora/wasm

# wrangler.toml
compatibility_flags = ["nodejs_compat"]

import { renderPdf, VelloraUnsupportedError } from "vellora";

export default {
  async fetch(request: Request): Promise<Response> {
    const html = `<!DOCTYPE html><html><body><h1>Hello, {{ name }}</h1></body></html>`;
    try {
      const pdf = await renderPdf(html, { name: "Workers" });
      return new Response(pdf, { headers: { "content-type": "application/pdf" } });
    } catch (err) {
      if (err instanceof VelloraUnsupportedError) {
        return Response.json({ feature: err.feature, line: err.line, col: err.col }, { status: 422 });
      }
      throw err;
    }
  },
};

The full example renders the sample invoice with its logo: examples/cloudflare-worker.

Same PDF, same errors

It is the same Rust engine: same HTML/CSS subset, same located errors, and the same PDF bytes as on Node.js for the same input. The repository's tests check that for every fixture.

What's different

• Size. The engine is a 14.9 MiB .wasm (6.1 MiB gzip), fonts included. Workers counts only the uncompressed bundle, up to 64 MiB on Free and Paid, so it fits both plans.
• Slower, one thread. A render runs on the Worker's thread. On the repository benchmark (benchmarks/wasm-vs-native.mjs, sample invoice, Node.js 22, one Linux machine), the warm median was 27.2 ms for WebAssembly against 22.1 ms native, and the first render in a fresh process 325 ms against 38 ms: V8 compiles the engine's code the first time it runs. Measure on your own templates.
• No strict: false, no Chrome. The fixers behind strict: false use a native addon, and there is no browser on Workers: both reject with VelloraInputError. Run vellora fix on your templates at build time instead.

Details: the "WebAssembly build" section of the compatibility matrix.