Preview
Preview containers let you see your project running live in the browser. Each preview launches a Docker container with the appropriate framework runtime.
Starting a Preview#
From the Command Center right panel, click Start Preview. The system:
- Builds a container from the framework-specific Docker image
- Runs the install command (if configured)
- Starts the dev server with the framework's default command
- Configures a reverse proxy for browser access
No manual port forwarding is needed — the reverse proxy handles routing automatically.
Preview States#
| State | Description |
|---|---|
| Idle | No preview container running |
| Loading | Container is starting up |
| Active | Preview is live and accessible |
Framework-Specific Behavior#
Each framework has a pre-configured Docker image and default start command (see Projects). You can override the start command in project settings.
Preview containers have resource limits:
- Memory: 128MB (static) to 512MB (all others)
- CPU: 0.25 (static) to 1.0 (all others)
Log Streaming#
While a preview is active, container logs (stdout and stderr) stream to the bottom panel via WebSocket. This shows:
- Build output and compilation errors
- Server startup messages
- Runtime errors and warnings
- Request logs
Sharing Previews#
Generate shareable links for your preview:
- Click Share while the preview is active
- Copy the generated link
- Share with anyone — no authentication required to view
Manage shares:
- List all active share links
- Revoke individual share links
- Share links become inactive when the preview container stops
Lifecycle#
- Idle timeout: Previews stop automatically after a period of inactivity (default 15 minutes on Free, 30 minutes on Starter, 2 hours on Pro — configurable by plan)
- Hard maximum: Previews are forcibly stopped after 8 hours regardless of activity
- Heartbeat: The frontend sends periodic heartbeats to keep the preview alive while you're actively viewing it
- Ephemeral: Each preview starts fresh — no state is preserved between sessions. The project workspace files persist, but the container environment is rebuilt each time.
Terminal Access#
When a preview container is running, you can open an interactive terminal inside it. See Terminal.