The JS document.cookie is a bad way of getting the cookies as we can not use it to get HttpOnly cookies such as most session cookies. Seems one of those PR's might fix this: https://github.com/fluttercommunity/flutter_webview_plugin/pull/608 (I have tested this, and it is working for me) https://github.com/fluttercommunity/flutter_webview_plugin/pull/588 (might be missing iOS)