How to Control File Downloads in JavaScript (ES6) PDF Viewer

17 Aug 20261 minute to read

Use the downloadStart event to intercept the start of a viewer download and optionally cancel it. Set args.cancel = true in the event handler to prevent the download.

• Include the JavaScript PDF Viewer script and the Download/Toolbar modules if the download feature is used.
• Ensure the viewer instance is initialized before assigning the downloadStart handler.

viewer.downloadStart = (args: any) => {
    // Custom logic
    args.cancel = true; // Prevent download action
};

By default, args.cancel is false, so the download proceeds unless explicitly canceled.

Flexibility

Leverage the [downloadStart] (https://ej2.syncfusion.com/documentation/api/pdfviewer/#downloadstart) event to apply custom rules for allowing or preventing downloads based on application logic.