React PDF Kit Worker Config

react-pdf-kit-worker-config

Use this skill when: the developer needs to override the pdfjs-dist version (for example, pinning to 4.10.38 for specific compatibility requirements) or point the PDF.js worker at a custom URL. This is the single home for all worker and pdfjs-dist configuration; the setup and framework skills deliberately contain none.

Default: zero configuration

In v2, @react-pdf-kit/viewer ships pdfjs-dist as a peer dependency pinned to 5.4.530, and RPConfig configures the worker automatically. For the common case you install only the viewer and do nothing else — no pdfjs-dist install, no workerUrl. Reach for the recipes below only when you must change the pdfjs-dist version or serve the worker from a custom location.

Gotchas

• Override through the workerUrl prop, not GlobalWorkerOptions. Pass <RPConfig workerUrl="...">; RPConfig applies it. Setting pdfjs.GlobalWorkerOptions.workerSrc by hand fights the library's own setup.
• Changing the pdfjs-dist version is a two-part job: install the version AND add a package-manager override, otherwise a transitive copy of the default version can win.
• Match the worker file to the installed version. A workerUrl pointing at a different pdfjs-dist build than the one resolved at runtime causes version-mismatch errors.
• Downgrading below 4.10.38 is not supported and can break viewer functionality. 4.10.38 is the documented floor; 5.4.530 is the default. Note: @react-pdf-kit/viewer ships polyfills so v5 works across supported browsers — prefer v5 unless you have a specific compatibility constraint that requires v4.

Procedure

Step 1 — Install the target pdfjs-dist and pin it

Install the version you want, then lock it with an override so every resolution uses it.

pnpm add pdfjs-dist@4.10.38     # example: pin to v4 for specific compatibility requirements

// package.json
{
  // pnpm:
  "pnpm": { "overrides": { "pdfjs-dist": "4.10.38" } },
  // npm:
  "overrides": { "pdfjs-dist": "4.10.38" },
  // yarn:
  "resolutions": { "pdfjs-dist": "4.10.38" }
}

Use the field that matches your package manager, then reinstall.

Step 2 — Point RPConfig at the matching worker

Pick the recipe for your bundler.

Vite

Add pdfjs-dist to optimizeDeps.include, then import the worker with Vite's ?url suffix and pass it to workerUrl:

// vite.config.ts
import { defineConfig } from 'vite'
export default defineConfig({
  optimizeDeps: { include: ['pdfjs-dist'] },
})

import { RPConfig } from '@react-pdf-kit/viewer'
import workerSrc from 'pdfjs-dist/build/pdf.worker.min.mjs?url'

export function Providers({ children }: { children: React.ReactNode }) {
  return <RPConfig workerUrl={workerSrc}>{children}</RPConfig>
}

TypeScript users: if ?url imports error, add a declaration file.

// global.d.ts
declare module '*?url' {
  const content: string
  export default content
}

Next.js 15+ (Turbopack)

Resolve the worker with the import.meta.url pattern and pass it to workerUrl in your client RPConfig wrapper:

// app/components/AppProviders.tsx
'use client'
import { RPConfig, type RPConfigProps } from '@react-pdf-kit/viewer'
import { type PropsWithChildren } from 'react'

const workerSrc = new URL(
  'pdfjs-dist/build/pdf.worker.min.mjs',
  import.meta.url
).toString()

export default function AppProviders({
  children,
  ...props
}: PropsWithChildren<Omit<RPConfigProps, 'workerUrl'>>) {
  return (
    <RPConfig workerUrl={workerSrc} {...props}>
      {children}
    </RPConfig>
  )
}

(See react-pdf-kit-nextjs-app-router for the surrounding client-only / dynamic-import structure.)

React + webpack

Copy the worker into your output with copy-webpack-plugin, then point workerUrl at the copied path:

// webpack.config.js
const CopyPlugin = require('copy-webpack-plugin')
module.exports = {
  plugins: [
    new CopyPlugin({
      patterns: [
        {
          from: 'node_modules/pdfjs-dist/legacy/build/pdf.worker.min.mjs',
          to: 'pdf.worker.min.mjs',
        },
      ],
    }),
  ],
}

<RPConfig workerUrl="/pdf.worker.min.mjs">{children}</RPConfig>

Alternative: CDN-hosted or self-hosted worker

workerUrl accepts any URL, so you can also serve the worker from a CDN or a fixed public path. Pin the URL to the exact installed pdfjs-dist version (never "latest"), and update your CSP worker-src to include that origin (or 'self' for a same-origin path).

Verify

pnpm install
pnpm build
pnpm dev   # or your equivalent serve step

In DevTools Network tab, filter for pdf.worker. You should see exactly one request, status 200, content-type application/javascript (or text/javascript). Open a PDF and confirm text selection works on a rendered page — that confirms the worker is answering PDF.js's calls, and that the worker build matches the installed pdfjs-dist.

References

• PDF.js worker docs: https://github.com/mozilla/pdf.js/wiki/Setup-PDF.js-in-a-website
• MDN worker-src: https://developer.mozilla.org/docs/Web/HTTP/Headers/Content-Security-Policy/worker-src
• Companion skills:
  • react-pdf-kit-setup: first-time setup (no worker config needed).
  • react-pdf-kit-nextjs14-pdfjs-override: Next.js 14 compatibility (v2 is unsupported on Next.js 14).