How to Enable Custom Script in SharePoint Online 365
Enabling the Custom Scripts is allowing the users to run the custom scripts on personal sites or created site collections. To use the embed script in sites we need to allow it first by using SharePoint designer.
Log in with Global admin in Office 365 Admin Portal Account and Follow the below approach to use custom script.
1 Click on top upper left App launcher then click “Admin”.
2 Now Click on “… Show all”.
3 Select “SharePoint”.
4 Click on the Settings icon.
5 And Click on “Go to the Classic setting page” Link.
6 Now you can find Custom Script setting on this page. Allow both (personal and self-service created sites) and Click on OK Button.
* It will take a maximum of 24 hours to update settings in the tenant.