Use the Canvas App Previewer to load and debug a canvas app inside Salesforce before you embed it anywhere. You need a defined canvas app and the right permissions first.
- Confirm your permissions
Make sure your user has Customize Application and Modify All Data. Without both, the Canvas App Previewer item does not appear in Setup. Most admins already have them.
- Open the Previewer
In Setup, type Canvas App Previewer into the Quick Find box and select it. The page lists the canvas apps defined in your org in the left-hand pane.
- Load your canvas app
Click your canvas app in the left-hand pane. It renders in the preview frame on the right, running as you, with a real Salesforce context payload.
- Debug and iterate
Use browser developer tools on the frame to inspect the signed request, the context, and any callbacks. Change the external app, refresh, and repeat until it behaves.
Signed request posts a signed payload the app verifies with the consumer secret; OAuth 2.0 runs an authorization flow then fetches context.
Available in Enterprise, Performance, Unlimited, and Developer editions, and in Professional with API access and Lightning Platform Canvas enabled.
The Previewer builds the context as the logged-in user, so the app receives user, org, environment, and where relevant record details.
- If the Previewer menu item is missing, the cause is almost always a missing Customize Application or Modify All Data permission, not a licensing problem.
- Signed-request verification failures on the app side usually trace to server clock skew or the wrong consumer secret, not to the Salesforce-side setup.
- The Previewer is a development surface only. Production access still depends on the connected app definition, the enabled locations, and user assignments.