Mintplex-Labs/anything-llm · error

Invalid file upload. ${err.message}

Error message

Invalid file upload. ${err.message}

What it means

Multer error handler in handleFileUpload: the multipart upload middleware rejected the request (file too large, unexpected field, etc.), and multer's err.message is wrapped into a 500 response describing the invalid upload.

Source

Thrown at server/utils/files/multer.js:97

      normalizePath(file.originalname)
    )}`;
    req.randomFileName = randomFileName;
    cb(null, randomFileName);
  },
});

/**
 * Handle Generic file upload as documents from the GUI
 * @param {Request} request
 * @param {Response} response
 * @param {NextFunction} next
 */
function handleFileUpload(request, response, next) {
  const upload = multer({ storage: fileUploadStorage }).single("file");
  upload(request, response, function (err) {
    if (err) {
      response
        .status(500)
        .json({
          success: false,
          error: `Invalid file upload. ${err.message}`,
        })
        .end();
      return;
    }
    next();
  });
}

/**
 * Handle API file upload as documents - this does not manipulate the filename
 * at all for encoding/charset reasons.
 * @param {Request} request
 * @param {Response} response
 * @param {NextFunction} next
 */

View on GitHub (pinned to 3aec848f28)

Solutions

1. Read err.message in the response — multer rejected the upload (e.g. file too large or bad multipart body).
2. Reduce the file size below the upload limit or raise the multer limits in fileUploadStorage.
3. Ensure the request is multipart/form-data with the file in the 'file' field.
4. Check the server storage directory exists and is writable.

When it happens

Trigger: Multer file upload validation failed. Triggered when an uploaded file fails type/size/extension checks in the generic file upload filter (multer.js:97).

Common situations: See trigger scenarios.

AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18). Data as JSON: /api/errors/fc79102e5e8e100a. Report an issue: GitHub.