The above Todo example is taken pretty much verbatim from vuejs.org/guide.
Modern Web application all suffer from a blank screen problem. The framework code needs to be loaded, then the application, and only then the DOM is updated with actual content.
To fully appreciate the experience, we simulate the network delays by delaying the vue.js and application loading by 2 seconds. Notice that during the loading delay the user sees a blank white page (bad).
Turn the "Hydration" by checking the box below and reload the page. You should see the items as you had them before almost immediately. This is "dry" HTML snapshot saved into localStorage and loaded by a tiny piece of code "hydration.js" as the page loads. The "dry" HTML will be shown while the Vue.js library and the app code is being loaded; the switch from "dry" to full app will happen automatically.
Use hydration: Clear local storage