Validating File Types and Sizes

Rename a text file from notes.txt to photo.png, upload it, and a common Multer filter accepts it as an image. The configuration below allows JPEG, PNG and PDF attachments up to 2 MB, and the test sent it 33 bytes of plain text named photo.png:

const ALLOWED_TYPES = ["image/jpeg", "image/png", "application/pdf"];

const upload = multer({
  dest: "uploads/",
  limits: { fileSize: 2 * 1024 * 1024, files: 1 },
  fileFilter: (req, file, cb) => {
    if (ALLOWED_TYPES.includes(file.mimetype)) {
      cb(null, true);
    } else {
      cb(null, false);
    }
  },
});

``