How to add a custom field in an Attachment Object?

Salesforce Attachment and Notes object are not customizable so that we can’t create a custom field in Attachment and Notes Object.

View Account/Case/ Custom Pa page layout then you will see “the list is not customizable.” for notes and attachement.

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Salesforce MVP | Lightning Champion | 16x Salesforce Certified | Application Architect | 6x Trailhead Ranger | Techforce Services | Australia