The live preview
What the preview shows, who you are signed in as, device widths, refreshing, opening it in a tab, and what the builder can see of it.
Last updated September 17, 2026
On this page
The preview is your app, running, in the right half of the builder. It turns on when the first build compiles and refreshes in place after every change.
You are signed in as the owner
Inside the preview you are automatically signed in to your own app as an admin user, so screens behind a login, admin-only pages and your own data all work without registering. A real visitor arrives signed out; ask the builder to show you the signed-out view, or open the published address in a private window.
Controls
| Control | What it does |
|---|---|
| Desktop, Tablet, Mobile | Resizes the preview to each width. Every app is built responsive; this is where you check it. |
| Refresh | Reloads the preview. Useful after you change data in the Database tab. |
| Open in a new tab | Opens the preview full size in its own tab, still signed in as you. |
| Address bar | Shows the page you are on. Type a path to jump to it. |
| Preview, Dashboard | Switches the right half between the running app and its dashboard. |
What the builder can see
The builder can take its own screenshot of the preview to check its work, and it receives a report of anything your browser saw go wrong on the page since your last message. So if a page renders blank or a button fails, say so; it usually already has the details.
Preview and published are different
The preview always shows the latest build. Visitors see the version you last published. Nothing you do in the builder reaches visitors until you publish again. See Version history and Publishing.