Hi @Ching Song Lim ,
Welcome to Q&A forum!
You can add the "Clear-Site-Data" security header to a SharePoint 2019 site:
- Open Internet Information Services (IIS) Manager on the SharePoint server.
- Select the website that you want to add the header to.
- Click on the "HTTP Response Headers" feature.
- Click on "Add" in the right-hand pane to add a new header.
- In the "Name" field, enter "Clear-Site-Data".
- In the "Value" field, enter the types of data that you want to clear. For example, you can enter "cookies, cache, storage" to clear cookies, cache, and local storage data.
- Click "OK" to save the new header.
Once you have added the "Clear-Site-Data" header, web browsers will be instructed to clear the specified types of data when a user navigates away from the SharePoint site.
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