Before automating the creation of subsites or sites in SharePoint Online, it’s necessary to have a template available. In the modern model, templates are based on Site Designs and Site Scripts.

🏗️ Creating and Registering a SharePoint Site Template (Site Design)

📌 Introduction

This section explains how to build and register a template from scratch, using PowerShell commands against a tenant such as Contoso.

⚙️ Step 1 – Define a Site Script

A Site Script is a JSON file that describes actions SharePoint should execute when the template is applied.

Example (ContosoProjectScript.json):

{
  "$schema": "schema.json",
  "actions": [
    {
      "verb": "createSPList",
      "listName": "ProjectDocuments",
      "templateType": 101,
      "subactions": [
        {
          "verb": "setDescription",
          "description": "Document library for project files"
        }
      ]
    },
    {
      "verb": "applyTheme",
      "themeName": "ContosoTheme"
    }
  ],
  "version": 1
}

This script creates a document library and applies a custom theme.

⚙️ Step 2 – Upload the Site Script

Use SharePoint Online PowerShell (or PnP PowerShell).

# Connect to tenant
Connect-SPOService -Url https://contoso-admin.sharepoint.com

# Upload the script content
$script = Add-SPOSiteScript `
  -Title "Contoso Project Script" `
  -Description "Creates project library and applies Contoso theme" `
  -Content (Get-Content .\ContosoProjectScript.json -Raw)

This returns a GUID for the Site Script.

⚙️ Step 3 – Create a Site Design

Now link the script to a Site Design (the actual template).

Add-SPOSiteDesign `
  -Title "Contoso Project Template" `
  -WebTemplate "64" `
  -SiteScripts $script.Id `
  -Description "Template for Contoso project collaboration sites"

Title → The friendly name (e.g., “Contoso Project Template”).
WebTemplate “64” → Indicates it applies to a Team site.
SiteScripts → The GUID(s) of scripts to execute.

The command returns another GUID, which is the Site Design ID (the value you will later use in automation flows).

⚙️ Step 4 – Verify the Template

List the available templates with:

Get-SPOSiteDesign

Expected output:

Id                                   Title                      WebTemplate
----------------------------------- -------------------------- ------------
12345678-90ab-cdef-1234-567890abcdef Contoso Project Template   64

✅ Key Takeaways

Site Scripts are JSON definitions of actions.
Site Designs are published templates that reference one or more scripts.
They are stored in the tenant’s catalog and identified by a GUID.
These GUIDs are what you use in Power Automate or REST API calls to create subsites/sites automatically.