How to display field value in the web version of my campaign
When you use merge tags in your campaigns, the value for every merge tag will differ for each subscriber. However, in the web version of your campaign, merge tags will be replaced with generic placeholders – for example, {{PetName}} will be displayed as <<Pet Name>>.
Using the PetName field as an example, if my subscriber's PetName value is Bao, this is how it'll display in their inbox:
But the web version won't include their specific field values as it needs to be the same for everybody so instead, you'll see the merge tag there:
If you’d like to make sure that your merge tag in the web version of your campaign contains a specific value, rather than a placeholder, you’d need to set its default value.
To do it, go to the Lists tab, pick your list and click on the Fields tab. Find the custom field you want to edit and add its default value.
Once it's done, you'll see your default value in the web version of your campaign: