Block preview window
Block preview is a preview window that shows the block's output in real time. It is the same on the settings screens of recommendation and dynamic blocks, and you open it with the «Open in modal» button.
Why you need it
While you configure a block (strategy, filters, audience), you want to know right away which products these settings will put in the output. Block preview lets you check this without publishing the block on the site and without leaving the admin panel.
Basic tab: product list
The window has three tabs: Basic | Explanation | Investigate.
The first tab, Basic, shows a table of the products that the block will output with the current settings:
- Products load automatically as you scroll down the table.
- The table shows card previews (name, image, marker, brief metadata).
- For the Similar products block, the preview is built from the saved block, and the screen shows the hint "The preview is generated based on the saved block — form changes will be applied after saving". To see the result of your changes, save the block first.
Explanation tab: why a product is in the output
The second tab, Explanation, answers the question "why did this particular product end up in the block". Under each product card, badges show the reasons it was selected, for example "Ordered together", "Matching attributes", "In the same section", "In the popular ranking", "Viewed", or "Substituted as popular".
The badges are ordered by meaning: first output substitution (fallback to popular products), then selection (why the product is here at all), then ranking (why it is in this position), and finally demotion (for example, "Lower — price difference" means the product was moved down because of a price difference).
Explanation explains the output per product: what applied to a specific card. Investigate shows the picture for the request as a whole: which audience rule was applied, what warnings the system returned, and whether fallback was enabled. If there are no selection reasons, the tab shows a message such as "No data for explanation". This is normal, for example, for an empty preview.
Investigate tab: diagnostics
The third tab, Investigate, is for debugging. It shows what happened under the hood while the output was being built:
| Section on screen | What it means |
|---|---|
| Audience rule applied | The audience rule that applied to the current request. See Audience Filter (opens in a new tab). |
| Warnings | Diagnostics, for example "the attribute set is empty" or "fallback selected products outside the chosen category". |
| Fallback used | A flag that shows whether the fallback path ran (backup display of trending products). |
| Request context | What the system received when building the preview (user ID, cart, selected categories, and so on). |
If a section has no data, the Investigate tab doesn't show it. This is not an error.
Simulate user (ID): preview as a specific user
In the Context for preview section of the block settings screen, you set the context the preview is built for. The field depends on the block type:
| Block type | Preview context field |
|---|---|
| Trending, Recently viewed, Personal recommendations, Repeat purchase | Simulate user (ID) |
| Cart complement, Cart similar | Test cart (product IDs) |
| Wishlist similar | Test wishlist (product IDs) |
| Frequently ordered, Similar products (automatic mode) | Test product ID |
For personalized blocks, the field is Simulate user (ID) (the Investigate tab diagnostics refer to the same value as simulatedUserId). Enter the ID of any user, and the preview builds the result as if the request came from that user. Use it to:
- Check personal recommendations (Personal recommendations, Repeat purchase) for a specific customer.
- Reproduce a complaint like "my block shows the wrong products": enter the customer's ID and see what they see.
If you don't specify Simulate user (ID), the preview uses your own admin context, and personalized blocks may return empty or irrelevant output.
The blocks.preview access right
Access to block preview is controlled by a separate right, blocks.preview, in the rights tree (opens in a new tab).
This lets you:
- Give a role that edits blocks no access to the preview (for example, form-only content managers).
- Hide from some admins sensitive data that Investigate may expose (the Request context section).
Grant blocks.preview to those who configure and check block output. Grant it to content managers only if they need to see the block's actual output before publication.