How can I get the siteId of the current site with Microsoft Graph API?

On classic sites using spPageContextInfo:

(location.host + "," + _spPageContextInfo.siteId + "," + _spPageContextInfo.webId).replace(/[\{\}]/g, "")

Try this: https://graph.microsoft.com/v1.0/sites/{hostname}:/sites/{path}?$select=id For example: https://graph.microsoft.com/v1.0/sites/cie493742.sharepoint.com:/sites/Contoso/Operations/Manufacturing?$select=id (this one you can try on the Graph Explorer.

What you get back in the id is in this format:

{hostname},{spsite.id},{spweb.id}

For more info here is the link to the docs: https://developer.microsoft.com/en-us/graph/docs/api-reference/v1.0/api/site_get

Another way you can get the Site-id by below Graph Http Get API.

https://graph.microsoft.com/v1.0/sites

You don't need to do a Graph API call to get the siteId of the current site. It is available in the PageContext.

In the main class of your webpart you can find it at:

this.context.pageContext.site.id