The hover preview is not edited in one place anymore. In Lightning Experience you shape it through the object's Compact Layout; in Salesforce Classic you shape it through the page layout's Mini Page Layout and the org-level Enable Hover Details switch. These steps cover both so you can configure whichever UI your org runs.
- Decide which UI you are configuring
If your org runs Lightning Experience, you will edit a Compact Layout. If it runs Classic, you will edit a Mini Page Layout and confirm the Enable Hover Details setting. The hover content does not come from the same place in both, so identify the UI first.
- Lightning: edit the Compact Layout
Go to Setup, Object Manager, pick the object (for example Contact or Case), and click Compact Layouts. Edit the primary Compact Layout or create one and assign it as primary. Add the fields you want and order them; the first field becomes the hover title.
- Classic: enable hover details and set the Mini Page Layout
In Classic, confirm Setup, Customize, User Interface, Enable Hover Details is checked. Then open the object's page layout, click Mini Page Layout in the header, and choose the fields and related lists that should appear in the hover popup.
- Test as a restricted user
Field-level security removes hidden fields from the popup. Log in as, or impersonate, a user on your most restricted relevant profile and hover a record. Confirm the preview shows the fields you intended and is not sparse or blank for that profile.
The single source for the Lightning hover, the Highlights Panel, the mobile record view, and search results. Editing it changes all of those at once.
The per-page-layout configuration that defines Classic hover content. Found inside each page layout, separate from the Lightning Compact Layout.
The org-level switch under Setup, Customize, User Interface that turns Classic hover popups on or off everywhere.
Controls the title and top five fields of the Case hover in Lightning; the description and latest update sections are filled automatically and cannot be customized.
- The Lightning hover and the Highlights Panel read the same Compact Layout, so you cannot change one without changing the other.
- Mini Page Layout settings do not copy into the Compact Layout when an org moves to Lightning; rebuild the intent rather than expecting it to migrate.
- A field hidden by field-level security disappears from the hover with no placeholder, which can make a popup look broken for restricted profiles.
- Touch devices do not hover, so tablet and mobile users tap into the record instead of seeing a preview; do not design workflows that depend on hovering.