# Fields, page layouts and field deletion impacts

*Platform Administrator Study Guide · Object Manager and Lightning App Builder · Last updated September 26, 2026 · https://certifyforce.com/study-guide/platform-administrator/object-manager-and-lightning-app-builder/fields-page-layouts-and-field-deletion-impacts*

How to create and change custom fields (required, unique, external ID, roll-up summary, cross-object formula, dependent picklists), what page layouts, compact layouts and field-level security each control, and what happens when a field is deleted, restored or has its type changed.

- Certification: Salesforce Platform Administrator
- Exam section: Object Manager and Lightning App Builder
- Study guide: https://certifyforce.com/study-guide/platform-administrator

**Official exam objective:**

> Explain how to create, delete, and customize fields and page layouts on standard and custom objects, and know the implications of deleting fields (roll-up summaries, cross object formulas, picklist dependencies, relationship fields).

## What the exam expects

- Choose the right field type and attributes for a requirement: roll-up summary, cross-object formula, universally required, unique and external ID.
- Configure dependent picklists and know which fields can control and which can depend.
- Separate what a page layout controls from what field-level security and compact layouts control.
- Predict what deleting a field does, including roll-up summaries, cross-object formulas, picklist dependencies and relationship fields, and how to restore it.
- Anticipate the risks of changing a custom field's data type.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Deleted custom field retention | Restorable with its data for 15 days | [Delete Custom Fields](https://help.salesforce.com/s/articleView?id=platform.deleting_fields.htm&type=5) |
| Delete permissions | Customize Application and View All Data | [Delete Custom Fields](https://help.salesforce.com/s/articleView?id=platform.deleting_fields.htm&type=5) |
| Field referenced by another field | Can't be deleted until the reference is removed | [Delete Custom Fields](https://help.salesforce.com/s/articleView?id=platform.deleting_fields.htm&type=5) |
| Field history on delete | History data deleted; tracking stops | [Delete Custom Fields](https://help.salesforce.com/s/articleView?id=platform.deleting_fields.htm&type=5) |
| Restored field attributes | Unique and required removed; dependencies removed | [Restore Deleted Fields](https://help.salesforce.com/s/articleView?id=platform.fields_manually_restore_attributes.htm&type=5) |
| Deleted relationship field | Converted to a lookup if restored | [Restore Deleted Fields](https://help.salesforce.com/s/articleView?id=platform.fields_manually_restore_attributes.htm&type=5) |
| Required in field definition | Enforced everywhere in Salesforce, including the API | [Field Attributes](https://help.salesforce.com/s/articleView?id=platform.custom_field_attributes.htm&type=5) |
| External ID fields per object | Up to 25 (Unique fields count toward it) | [Field Attributes](https://help.salesforce.com/s/articleView?id=platform.custom_field_attributes.htm&type=5) |
| Roll-up summary types | COUNT, SUM, MIN, MAX, with optional filter criteria | [Roll-Up Summary](https://help.salesforce.com/s/articleView?id=platform.fields_about_roll_up_summary_fields.htm&type=5) |
| Multi-select picklist | Dependent only, never controlling | [Dependent Picklists](https://help.salesforce.com/s/articleView?id=platform.fields_dependent_field_considerations.htm&type=5) |
| Checkbox | Controlling only, never dependent | [Dependent Picklists](https://help.salesforce.com/s/articleView?id=platform.fields_dependent_field_considerations.htm&type=5) |
| Controlling field values | Up to 300 | [Dependent Picklists](https://help.salesforce.com/s/articleView?id=platform.fields_dependent_field_considerations.htm&type=5) |
| Highlights panel (Lightning Experience) | First seven compact layout fields | [Compact Layouts](https://help.salesforce.com/s/articleView?id=platform.compact_layout_overview.htm&type=5) |
| Layout versus field-level security | Most restrictive setting applies | [Field Permissions](https://help.salesforce.com/s/articleView?id=platform.users_profiles_field_perms.htm&type=5) |

## Check yourself

- Which two permissions are needed to delete a custom field, and for how long can it be restored?
- Why must an admin revisit a field after restoring it?
- Where does a roll-up summary field live, and which four calculation types does it offer?
- Which field types can act as a controlling field for a dependent picklist?
- When a page layout marks a field required but field-level security makes it read-only, which setting wins?

## Sources

- [Delete a Custom Field](https://help.salesforce.com/s/articleView?id=platform.deleting_fields.htm&type=5)
- [Roll-Up Summary Field](https://help.salesforce.com/s/articleView?id=platform.fields_about_roll_up_summary_fields.htm&type=5)
- [Considerations for Converting the Field Type of a Custom Field](https://help.salesforce.com/s/articleView?id=platform.notes_on_changing_custom_field_types.htm&type=5)
- [Dependent Picklist Considerations](https://help.salesforce.com/s/articleView?id=platform.fields_dependent_field_considerations.htm&type=5)
- [Field Permissions](https://help.salesforce.com/s/articleView?id=platform.users_profiles_field_perms.htm&type=5)
- [Custom Field Attributes](https://help.salesforce.com/s/articleView?id=platform.custom_field_attributes.htm&type=5)
- [Compact Layouts](https://help.salesforce.com/s/articleView?id=platform.compact_layout_overview.htm&type=5)
- [Manually Restore Attributes of Deleted Fields](https://help.salesforce.com/s/articleView?id=platform.fields_manually_restore_attributes.htm&type=5)
- [Considerations for Object Relationships](https://help.salesforce.com/s/articleView?id=platform.relationships_considerations.htm&type=5)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 16 linked practice questions, and unlimited timed mock exams are included with the Platform Administrator pack (USD $19): https://certifyforce.com/practice-exams