Preview in Browser
Preview in Browser opens your current page in a browser tab instantly — no server required. It is the fastest way to check a page’s visual appearance and basic layout while you work.
The browser preview button
Click the browser preview button (the open-in-browser arrow icon) in the top toolbar, or press F5 . Site Designer saves the page, writes a temporary HTML file to disk, and opens it in your default browser.
The browser address bar shows a file:// path pointing to that temporary file — for example:
file:///C:/Users/YourName/AppData/Local/Temp/sd-preview/index.html
Preview in Browser vs. Live Preview
These two tools serve different purposes:
| Preview in Browser | Live Preview | |
|---|---|---|
| Protocol | file:// (direct file open) | http://localhost (local server) |
| Speed to open | Instant | 1–3 seconds to start server |
| JavaScript | Basic scripts work; modules may not | Full JS support including ES modules |
| Forms | Renders visually; submit won’t POST | Can test form submissions |
| PHP | Not supported | Supported with XAMPP |
| Auto-reload on save | No | Yes |
| Best for | Quick visual checks | Testing interactions and dynamic features |
Use Preview in Browser when you want a fast sanity check — does the layout look right? Is the typography correct? Are the images loading?
Use Live Preview when you need to test actual behavior — does the form validate? Does that JavaScript slider work? Does the PHP contact form send email?
Limitations of file:// previews
Opening a page over the file:// protocol restricts several browser capabilities:
- JavaScript ES modules (
import/export) are blocked due to CORS restrictions onfile:// - Fetch and XMLHttpRequest to other files are blocked in Chromium-based browsers
localStorageandsessionStoragemay behave differently- Service Workers require HTTPS and will not register from
file:// - External fonts linked via
@font-faceto relative paths may not load in all browsers
For any page that uses these features, switch to Live Preview instead.
The temporary file location
Site Designer writes preview files to a system temp directory. The exact location depends on your OS:
- Windows:
%LOCALAPPDATA%\Temp\sd-preview\ - macOS:
/var/folders/.../sd-preview/(a temp folder managed by the OS)
These files are overwritten each time you preview and are cleaned up automatically. Do not use this location to store or share your work.
Testing in multiple browsers
To test in a browser other than your system default:
- Preview the page normally — your default browser opens with the
file://URL. - Copy the full path from the address bar.
- Paste it into the address bar of another browser and press Enter .
Alternatively, start Live Preview and copy the http://localhost:PORT URL — that URL works in any browser on the same machine simultaneously.
