Standard VS Custom Reports

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Hi Everyone,

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How to check if reports are standard reports vs custom report?
I need a table that shows a reports is a standard report or a custom report, suppose i have created a report & stored it in the Custom folder, so I need the backend table that stores this details.
For example : We have a standard report : User Role Membership report, I need to know the backend table that shows it is a standard report.

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