How to make a field required at page layout level in Salesforce?

In Salesforce Classic
<div>For custom object:

1. Click on Setup.
2. Go to Quick Find and enter Object.
3. Choose the object.
4. Under the Custom Fields & Relationships, select the custom field that you will make required.
5. Click on Edit and under the General Options section select Required.
6. Click on Save.

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<div>For standard object:

1. Click on Setup.
2. Under Build section, click the dropdown button for Customize.
3. Click the dropdown button for the object and click on Fields.
4. Under the Custom Fields & Relationships, select the custom field that you will make required.
5. Click on Edit and under the General Options section select Required.
6. Click on Save.

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In Lightning Experience

1. Click on the gear icon then Setup > Object Manager.
2. Choose the object > Fields & Relationships.
3. Select the custom field that you will make required.
4. Click on Edit and under General Options select Required.
5. Click on Save.

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