How to add custom HTML/CSS to a sharepoint modern page

NS 20 Reputation points

I want to add some custom HTML/CSS script in a sharepoint modern page but I have not find a way to do so yet.

I have tried to upload my html script as .aspx and embed it using iframe.

I have tried to add a web part, there is no content editor.

I have created a wiki page, I tried to edit source, most of my code is being removed and I am getting a Warning: Some of your markup was stripped out. Please use the embed command>

I try to embed code, I am getting   

This HTML cannot be inserted because you don't have access to add scriptable Web Parts in this site. Please contact your administrator if you think you should have rights to do so.

Is there any workaround?

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Accepted answer
  1. RaytheonXie_MSFT 30,991 Reputation points Microsoft Vendor

    Hi @NS,

    As the script editor web part is not supported in modern SharePoint, we are unable to insert CSS or JavaScript directly. We have to use SPFx based react script editor web part to add custom CSS or JavaScript to modern SharePoint Online pages.


    1. Build your first SharePoint Framework Extension.
    2. Inject Custom CSS on SharePoint Modern Pages using SPFx Application Extensions.
    3. Step By Step Procedure To Add A JS File To All Pages In A SPFx Modern Pages Using SharePoint Framework Extension.

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