missing-elements · alekswebnet · Mar 6, 2026 · Mar 6, 2026 · Mar 6, 2026
diff --git a/README.md b/README.md
@@ -14,7 +14,7 @@ Supported in all [major browsers](https://caniuse.com/custom-elementsv1), and wo
 
 ## Features
 
-- Standalone web component with no runtime dependencies
+- Standalone isolated web component with no runtime dependencies
 - Drop-in, iframe-based PDF.js default viewer for any web app
 - Works with same-origin and cross-origin PDF documents
 - Configure via attributes and URL parameters (page, zoom, search, pagemode, locale)
@@ -86,8 +86,9 @@ The element is block-level and needs an explicit height.
 | `zoom` | Zoom level (for example `auto`, `page-width`, `200%`). | `''` |
 | `pagemode` | Sidebar mode: `thumbs`, `bookmarks`, `attachments`, `layers`, `none`. | `none` |
 | `locale` | Viewer UI locale (for example `en-US`, `de`, `uk`). [Available locales](https://github.com/mozilla/pdf.js/tree/master/l10n) | `''` |
+| `locale-src-template` | Locale file URL template. Must contain `{locale}` placeholder. Used together with `locale`. | `https://cdn.jsdelivr.net/gh/mozilla-l10n/firefox-l10n@main/{locale}/toolkit/toolkit/pdfviewer/viewer.ftl` |
 | `viewer-css-theme` | Viewer theme: `AUTOMATIC`, `LIGHT`, `DARK`. | `AUTOMATIC` |
-| `worker-src` | PDF.js worker URL override. | `https://cdn.jsdelivr.net/npm/pdfjs-dist@5.4.624/build/pdf.worker.min.mjs` |
+| `worker-src` | PDF.js worker URL override. | `<package-url>/pdf.worker.min.mjs` |
 
 Play with attributes on [API docs page](https://alekswebnet.github.io/pdfjs-viewer-element/#api).
 
@@ -101,6 +102,41 @@ Most attributes can be updated dynamically:
 - `worker-src` updates viewer options for subsequent document loads.
 - `locale` rebuilds the viewer so localization resources can be applied.
 
+## Worker source
+
+By default, the component resolves `worker-src` to the worker shipped with this package (`pdf.worker.min.mjs` in `dist`).
+
+Set `worker-src` only if you want to serve the worker from a custom location (for example your own CDN or static assets path).
+
+- The URL must point to a valid PDF.js module worker file.
+- The worker version should match the bundled PDF.js version.
+
+```html
+<pdfjs-viewer-element
+  src="/file.pdf"
+  worker-src="https://cdn.jsdelivr.net/npm/pdfjs-dist@5.5.207/build/pdf.worker.min.mjs">
+</pdfjs-viewer-element>
+```
+
+## Locale source template
+
+Use `locale-src-template` when you need to load localization files from a custom host.
+
+- The template must include `{locale}`.
+- `{locale}` is replaced by the `locale` attribute value (for example `de`, `uk`, `en-US`).
+- If `locale` is not set, no locale file is loaded.
+- Changes to `locale-src-template` are applied when the viewer is (re)initialized, for example after setting/changing `locale`.
+
+Example:
+
+```html
+<pdfjs-viewer-element
+  src="/file.pdf"
+  locale="de"
+  locale-src-template="https://cdn.example.com/pdfjs-locales/{locale}/viewer.ftl">
+</pdfjs-viewer-element>
+```
+
 ## Viewer CSS theme
 
 Use `viewer-css-theme` attribute to set light or dark theme manually:
@@ -213,7 +249,7 @@ You can also react to source changes dynamically:
 
 ```javascript
 const viewerElement = document.querySelector('pdfjs-viewer-element')
-viewer.setAttribute('src', '/another-file.pdf')
+viewerElement.setAttribute('src', '/another-file.pdf')
 ```
 
 ## Accessibility

diff --git a/demo/custom-worker-src.html b/demo/custom-worker-src.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>pdfjs-viewer-element | Custom Worker Src Demo</title>
+    <script type="module" src="../dist/pdfjs-viewer-element.js"></script>
+    <style>
+      body {
+        margin: 0;
+        padding: 0;
+      }
+    </style>
+  </head>
+
+  <body>
+    <pdfjs-viewer-element
+      src="/public/sample-pdf-with-images.pdf"
+      worker-src="https://cdn.jsdelivr.net/npm/pdfjs-dist@v5.5.207/build/pdf.worker.min.mjs"
+      style="height: 100dvh">
+    </pdfjs-viewer-element>
+  </body>
+</html>
diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "pdfjs-viewer-element",
-  "version": "3.1.1",
+  "version": "3.1.2",
   "license": "MIT",
   "author": {
     "name": "Oleksandr Shevchuk",
@@ -37,7 +37,7 @@
   ],
   "scripts": {
     "dev": "vite",
-    "build": "tsc && vite build",
+    "build": "tsc && vite build && node scripts/copy-worker.mjs",
     "test": "vitest",
     "coverage": "vitest run --coverage"
   },
@@ -47,6 +47,7 @@
     "@vitest/browser": "^4.0.18",
     "@vitest/browser-webdriverio": "^4.0.18",
     "jsdom": "^28.1.0",
+    "terser": "^5.39.0",
     "typescript": "^5.9.3",
     "vite": "^7.3.1",
     "vitest": "^4.0.18",

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
diff --git a/scripts/copy-worker.mjs b/scripts/copy-worker.mjs
@@ -0,0 +1,26 @@
+import { mkdir, readFile, writeFile } from 'node:fs/promises'
+import { resolve } from 'node:path'
+import { minify } from 'terser'
+
+const rootDir = resolve(import.meta.dirname, '..')
+const sourceFile = resolve(rootDir, 'src', 'build', 'pdf.worker.mjs')
+const distDir = resolve(rootDir, 'dist')
+const targetFile = resolve(distDir, 'pdf.worker.min.mjs')
+
+await mkdir(distDir, { recursive: true })
+
+const workerCode = await readFile(sourceFile, 'utf8')
+const result = await minify(workerCode, {
+	module: true,
+	compress: true,
+	mangle: true,
+	format: {
+		comments: false
+	}
+})
+
+if (!result.code) {
+	throw new Error('Worker minification failed: empty output')
+}
+
+await writeFile(targetFile, result.code, 'utf8')
diff --git a/src/pdfjs-viewer-element.ts b/src/pdfjs-viewer-element.ts
@@ -1,4 +1,6 @@
-const PDFJS_VERSION = '5.5.207'
+const DEFAULT_WORKER_SRC = import.meta.env.DEV
+  ? new URL('./build/pdf.worker.mjs', import.meta.url).href
+  : new URL('./pdf.worker.min.mjs', import.meta.url).href
 
 const DEFAULTS = {
   src: '',
@@ -10,7 +12,8 @@ const DEFAULTS = {
   pagemode: 'none',
   locale: '',
   viewerCssTheme: 'AUTOMATIC',
-  workerSrc: `https://cdn.jsdelivr.net/npm/pdfjs-dist@${PDFJS_VERSION}/build/pdf.worker.min.mjs`
+  workerSrc: DEFAULT_WORKER_SRC,
+  localeSrcTemplate: 'https://cdn.jsdelivr.net/gh/mozilla-l10n/firefox-l10n@main/{locale}/toolkit/toolkit/pdfviewer/viewer.ftl'
 } as const
 
 export const ViewerCssTheme = { AUTOMATIC: 0, LIGHT: 1, DARK: 2 } as const
@@ -38,6 +41,13 @@ export class PdfjsViewerElement extends HTMLElement {
     ]
   }
 
+  private formatTemplate(template: string, params: Record<string, any>) {
+    return template.replace(/\{(\w+)\}/g, (_, key) => {
+      if (!(key in params)) throw new Error(`Missing param: ${key}`);
+      return String(params[key]);
+    });
+  }
+
   private getFullPath(path: string) {
     return path.startsWith('/') ? `${window.location.origin}${path}` : path
   }
@@ -120,8 +130,12 @@ export class PdfjsViewerElement extends HTMLElement {
       this.cleanupLocaleResource()
       return
     }
+    const localeUrl = this.formatTemplate(
+      this.getAttribute('locale-src-template') || DEFAULTS.localeSrcTemplate, 
+      { locale }
+    )
     const localeObject = {
-      [String(locale)]: `https://raw.githubusercontent.com/mozilla-l10n/firefox-l10n/main/${locale}/toolkit/toolkit/pdfviewer/viewer.ftl`
+      [String(locale)]: localeUrl
     }
     const localeLink = doc.createElement('link')
     localeLink.rel = 'resource'

diff --git a/types/pdfjs-viewer-element.d.ts b/types/pdfjs-viewer-element.d.ts
@@ -11,6 +11,7 @@ export declare class PdfjsViewerElement extends HTMLElement {
     private localeResourceLink?;
     private viewerStyles;
     static get observedAttributes(): string[];
+    private formatTemplate;
     private getFullPath;
     private getCssThemeOption;
     private applyIframeHash;

diff --git a/vite.config.ts b/vite.config.ts
@@ -11,7 +11,6 @@ export default defineConfig({
       output: {
         plugins: [
           terser({
-            'sourceMap': false,
             compress: true,
             mangle: false,
             format: { comments: false }