Pdfjs Errors Document

pdfjs-errors-document

Quick Reference

Document Error Types

Critical Warnings

ALWAYS wrap getDocument().promise in a try/catch -- document loading can throw any of the exception types above, and unhandled rejections cause blank pages with no user feedback.

ALWAYS check the name property of caught errors to distinguish between InvalidPDFException, MissingPDFException, PasswordException, and UnknownErrorException -- each requires a different recovery strategy.

NEVER swallow document loading errors with an empty catch block -- the user sees a blank page with no indication of what went wrong.

ALWAYS configure cMapUrl and set cMapPacked: true when loading PDFs that may contain CJK (Chinese, Japanese, Korean) text -- without CMaps, CJK characters render as blank rectangles.

ALWAYS set standardFontDataUrl when using pdfjs-dist 5.x -- PDF.js needs access to standard font data files for proper text rendering of PDFs that reference standard 14 fonts.

NEVER retry a PasswordException with the same password -- it will fail again. ALWAYS prompt the user for a new password before retrying.

Diagnostic Decision Tree

PDF document fails to load?
|
+-- InvalidPDFException
|   +-- File is 0 bytes? -> Download/upload failed, retry transfer
|   +-- File starts with "%PDF"? -> PDF is corrupt or truncated, re-obtain file
|   +-- File is actually HTML (404 page)? -> Server returned error page, fix URL
|   +-- File is a different format (DOCX, image)? -> Not a PDF, convert first
|
+-- MissingPDFException
|   +-- URL returns 404? -> Fix the URL path
|   +-- File was deleted? -> Handle gracefully, show "file not found" message
|   +-- Redirect to login page? -> Handle authentication before loading PDF
|   +-- Using relative URL? -> Use absolute URL or correct base path
|
+-- PasswordException
|   +-- code === PasswordResponses.NEED_PASSWORD? -> Prompt user for password
|   +-- code === PasswordResponses.INCORRECT_PASSWORD? -> Show "wrong password", reprompt
|   +-- Programmatic access needed? -> Pass password in getDocument({ password })
|
+-- Network / CORS error
|   +-- Mixed content (HTTP PDF on HTTPS page)? -> Serve PDF over HTTPS
|   +-- Cross-origin without CORS headers? -> Add CORS headers on PDF server
|   +-- Proxy available? -> Route PDF through same-origin proxy
|   +-- Fetch fails entirely? -> Check network, show offline message
|
+-- CJK text missing / blank characters
|   +-- cMapUrl not set? -> Set cMapUrl to cmaps directory path
|   +-- cMapPacked not true? -> Add cMapPacked: true to getDocument options
|   +-- CMap files not deployed? -> Copy cmaps/ from pdfjs-dist to public dir
|
+-- Font rendering issues
|   +-- standardFontDataUrl not set? -> Set path to standard_fonts directory
|   +-- Embedded font broken? -> PDF issue, not fixable in viewer
|   +-- Font files not deployed? -> Copy standard_fonts/ from pdfjs-dist
|
+-- Memory error / crash on large PDF
|   +-- PDF > 100 MB? -> Enable range requests (disableRange: false)
|   +-- Many high-res images? -> Reduce rendering scale
|   +-- Mobile device? -> Limit concurrent page renders
|
+-- UnknownErrorException
    +-- Check err.message for details -> May contain specific parser error
    +-- Reproducible with other PDFs? -> Likely a code issue, not PDF issue
    +-- Only this PDF? -> Likely a corrupt or unusual PDF structure

Essential Fixes

Fix 1: InvalidPDFException -- Corrupt or Non-PDF File

Error: InvalidPDFException: Invalid PDF structure

Cause: The loaded data is not a valid PDF. Common when a server returns an HTML error page instead of the PDF file, or the file is truncated.

import { getDocument, GlobalWorkerOptions } from "pdfjs-dist";

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

async function loadPdfSafely(source: string | ArrayBuffer) {
  try {
    const doc = await getDocument(
      typeof source === "string" ? { url: source } : { data: source }
    ).promise;
    return doc;
  } catch (err: unknown) {
    if (err instanceof Error && err.name === "InvalidPDFException") {
      throw new Error(
        "The file is not a valid PDF. It may be corrupt, truncated, " +
        "or the server returned an error page instead of the PDF file."
      );
    }
    throw err;
  }
}

Prevention: ALWAYS validate that the server response has Content-Type: application/pdf before passing data to getDocument(). If loading from user upload, check that the file starts with the %PDF magic bytes.

Fix 2: MissingPDFException -- File Not Found

Error: MissingPDFException: Missing PDF file.

Cause: The URL returned a 404 or the fetch failed entirely.

import { getDocument, GlobalWorkerOptions } from "pdfjs-dist";

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

async function loadPdfWithNotFoundHandling(url: string) {
  try {
    return await getDocument({ url }).promise;
  } catch (err: unknown) {
    if (err instanceof Error && err.name === "MissingPDFException") {
      throw new Error(
        `PDF file not found at "${url}". ` +
        "Verify the URL is correct and the file exists on the server."
      );
    }
    throw err;
  }
}

Fix 3: PasswordException -- Password-Protected PDF

Error: PasswordException with code: PasswordResponses.NEED_PASSWORD

Cause: The PDF is encrypted and requires a password to open.

import {
  getDocument,
  GlobalWorkerOptions,
  PasswordResponses,
} from "pdfjs-dist";

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

async function loadPasswordProtectedPdf(
  url: string,
  promptForPassword: () => Promise<string | null>
) {
  // First attempt: load without password
  try {
    return await getDocument({ url }).promise;
  } catch (err: unknown) {
    if (!(err instanceof Error) || err.name !== "PasswordException") {
      throw err;
    }

    // PDF requires a password -- prompt user
    const typedErr = err as Error & { code: number };

    if (typedErr.code === PasswordResponses.NEED_PASSWORD ||
        typedErr.code === PasswordResponses.INCORRECT_PASSWORD) {
      const password = await promptForPassword();
      if (!password) throw new Error("Password required but not provided.");

      // Retry with password
      try {
        return await getDocument({ url, password }).promise;
      } catch (retryErr: unknown) {
        if (retryErr instanceof Error &&
            retryErr.name === "PasswordException") {
          throw new Error("Incorrect password. Unable to open the PDF.");
        }
        throw retryErr;
      }
    }

    throw err;
  }
}

Fix 4: CORS / Network Errors

Error: Failed to fetch or Access to fetch blocked by CORS policy

Cause: The PDF is hosted on a different origin without CORS headers, or the page uses HTTPS while the PDF is served over HTTP (mixed content).

import { getDocument, GlobalWorkerOptions } from "pdfjs-dist";

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

// SOLUTION 1: Load through a same-origin proxy
async function loadPdfViaProxy(externalUrl: string) {
  const proxyUrl = `/api/pdf-proxy?url=${encodeURIComponent(externalUrl)}`;
  return await getDocument({ url: proxyUrl }).promise;
}

// SOLUTION 2: Fetch as ArrayBuffer with custom headers
async function loadPdfWithFetch(url: string) {
  const response = await fetch(url, {
    mode: "cors",
    credentials: "omit",
  });

  if (!response.ok) {
    throw new Error(`Failed to fetch PDF: ${response.status} ${response.statusText}`);
  }

  const data = await response.arrayBuffer();
  return await getDocument({ data }).promise;
}

Fix 5: Missing CMap Data for CJK Text

Error: CJK characters appear as blank rectangles or tofu characters.

Cause: PDF.js needs CMap (Character Map) files to decode CJK-encoded text. Without them, characters in Chinese, Japanese, or Korean PDFs render incorrectly.

import { getDocument, GlobalWorkerOptions } from "pdfjs-dist";

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

// ALWAYS configure CMap settings for CJK support
const doc = await getDocument({
  url: "/path/to/document.pdf",
  cMapUrl: new URL(
    "pdfjs-dist/cmaps/",
    import.meta.url
  ).toString(),
  cMapPacked: true,
}).promise;

Prevention: ALWAYS set cMapUrl and cMapPacked: true in getDocument() options. The CMap files are included in the pdfjs-dist/cmaps/ directory. For production, copy the cmaps/ directory to your public assets folder.

Fix 6: Font Loading Failures

Error: Text renders with wrong glyphs, missing characters, or falls back to default fonts.

Cause: PDF.js needs standard font data files for PDFs that reference the standard 14 PDF fonts without embedding them.

import { getDocument, GlobalWorkerOptions } from "pdfjs-dist";

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

// ALWAYS set standardFontDataUrl for proper font rendering
const doc = await getDocument({
  url: "/path/to/document.pdf",
  standardFontDataUrl: new URL(
    "pdfjs-dist/standard_fonts/",
    import.meta.url
  ).toString(),
  cMapUrl: new URL(
    "pdfjs-dist/cmaps/",
    import.meta.url
  ).toString(),
  cMapPacked: true,
}).promise;

Prevention: Production-Ready Document Loading

import {
  getDocument,
  GlobalWorkerOptions,
  PasswordResponses,
} from "pdfjs-dist";
import type { PDFDocumentProxy } from "pdfjs-dist";

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

interface LoadOptions {
  url: string;
  password?: string;
  onPasswordRequired?: () => Promise<string | null>;
  onError?: (type: string, message: string) => void;
}

async function loadDocument(options: LoadOptions): Promise<PDFDocumentProxy> {
  const { url, password, onPasswordRequired, onError } = options;

  try {
    return await getDocument({
      url,
      password,
      cMapUrl: new URL("pdfjs-dist/cmaps/", import.meta.url).toString(),
      cMapPacked: true,
      standardFontDataUrl: new URL(
        "pdfjs-dist/standard_fonts/",
        import.meta.url
      ).toString(),
    }).promise;
  } catch (err: unknown) {
    if (!(err instanceof Error)) throw err;

    switch (err.name) {
      case "InvalidPDFException":
        onError?.("invalid", "The file is not a valid PDF.");
        throw err;

      case "MissingPDFException":
        onError?.("missing", `PDF not found at "${url}".`);
        throw err;

      case "PasswordException": {
        const typedErr = err as Error & { code: number };
        if (onPasswordRequired &&
            (typedErr.code === PasswordResponses.NEED_PASSWORD ||
             typedErr.code === PasswordResponses.INCORRECT_PASSWORD)) {
          const pw = await onPasswordRequired();
          if (pw) return loadDocument({ ...options, password: pw });
          onError?.("password", "Password is required to open this PDF.");
        }
        throw err;
      }

      default:
        onError?.("unknown", `Failed to load PDF: ${err.message}`);
        throw err;
    }
  }
}

Reference Links

• references/methods.md -- Exception types, error codes, PasswordResponses enum, getDocument error-related options
• references/examples.md -- Error handling patterns, password prompt workflows, fallback strategies
• references/anti-patterns.md -- Common mistakes: swallowing errors, not handling passwords, missing CMap config

Official Sources

• https://mozilla.github.io/pdf.js/api/ -- PDF.js API reference (exception types)
• https://github.com/mozilla/pdf.js -- Source code (exception definitions in src/shared/util.js)
• https://github.com/mozilla/pdf.js/tree/master/examples -- Official examples with error handling