mozilla/pdf.js · error · Error

The API version "${apiVersion}" does not match the Worker ve

Error message

The API version "${apiVersion}" does not match the Worker version "${workerVersion}".

What it means

Error "The API version "${apiVersion}" does not match the Worker version "${workerVersion}"." thrown in mozilla/pdf.js.

Source

Thrown at src/core/worker.js:124

    }
  }

  static createDocumentHandler(docParams, port) {
    // This context is actually holds references on pdfManager and handler,
    // until the latter is destroyed.
    let pdfManager;
    let terminated = false;
    let cancelXHRs = null;
    const WorkerTasks = new Set();
    const verbosity = getVerbosityLevel();

    const { docId, apiVersion } = docParams;
    const workerVersion =
      typeof PDFJSDev !== "undefined" && !PDFJSDev.test("TESTING")
        ? PDFJSDev.eval("BUNDLE_VERSION")
        : null;
    if (apiVersion !== workerVersion) {
      throw new Error(
        `The API version "${apiVersion}" does not match ` +
          `the Worker version "${workerVersion}".`
      );
    }

    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
      // Fail early, and predictably, rather than having (some) fonts fail to
      // load/render with slightly cryptic error messages in environments where
      // the `{Object, Array}.prototype` has been *incorrectly* extended.
      //
      // PLEASE NOTE: We do *not* want to slow down font parsing by adding
      //              `Object.hasOwn` checks all over the code-base.
      const buildMsg = (type, prop) =>
        `The \`${type}.prototype\` contains unexpected enumerable property ` +
        `"${prop}", thus breaking e.g. \`for...in\` iteration of ${type}s.`;

      for (const prop in {}) {
        throw new Error(buildMsg("Object", prop));

View on GitHub (pinned to 5903d58d58)

Solutions

1. Load the matching pdf.worker build: the API (pdf.js) version and the worker (pdf.worker.js) version must be identical.
2. If using a bundler or CDN, pin both files to the same pdfjs-dist release and clear any stale cached worker file.

When it happens

Trigger: Thrown at src/core/worker.js:124 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/205f7666710d209c. Report an issue: GitHub.