Introduction to Microsoft Graph API

Microsoft Graph API is a unified endpoint that allows developers to access data, intelligence, and insights across Microsoft 365 services.
With a single endpoint (https://graph.microsoft.com), you can connect to resources such as:

• Outlook Mail, Calendar, and Contacts
• Microsoft Teams
• OneDrive & SharePoint files
• Azure Active Directory users and groups
• Intune device management

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Why Use Microsoft Graph API?

• Single Endpoint: No need to call multiple APIs for different services.
• Secure: Integrates with Azure Active Directory (Azure AD) for authentication and authorization.
• Powerful: Access to rich data across productivity, identity, and security tools.
• Extensible: Build applications that integrate seamlessly with Microsoft 365 ecosystem.

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Authentication

To use Microsoft Graph API, you must register your application in Azure Active Directory and obtain an access token.

1. Go to Azure Portal
2. Register a new app in Azure Active Directory
3. Configure Redirect URI and permissions (delegated or application)
4. Use OAuth 2.0 to acquire tokens

Example token request (using OAuth 2.0):

POST https://login.microsoftonline.com/{tenant}/oauth2/v2.0/token
Content-Type: application/x-www-form-urlencoded

client_id=YOUR_CLIENT_ID
&scope=https%3A%2F%2Fgraph.microsoft.com%2F.default
&client_secret=YOUR_CLIENT_SECRET
&grant_type=client_credentials

Example Requests Get User Profile

GET https://graph.microsoft.com/v1.0/me
Authorization: Bearer {access_token}

List Emails

GET https://graph.microsoft.com/v1.0/me/messages
Authorization: Bearer {access_token}

Send an Email

POST https://graph.microsoft.com/v1.0/me/sendMail
Content-Type: application/json
Authorization: Bearer {access_token}

{
  "message": {
    "subject": "Hello from Microsoft Graph API",
    "body": {
      "contentType": "Text",
      "content": "This email was sent using Microsoft Graph API!"
    },
    "toRecipients": [
      {
        "emailAddress": {
          "address": "example@domain.com"
        }
      }
    ]
  }
}

Best Practices

• Use Microsoft Authentication Library (MSAL) for handling tokens.
• Always request the least privileged permissions your app needs.
• Cache tokens to avoid unnecessary authentication requests.
• Monitor API usage with the Microsoft Graph Explorer tool.

Conclusion

Microsoft Graph API empowers developers to build intelligent apps that integrate with Microsoft 365, enabling collaboration, automation, and secure access to enterprise data. Start experimenting today using the official Graph Explorer.