Social Login in .NET: How to Add Google OAuth to Your SaaS
Adding Google (or similar) social login is table stakes for user-centric SaaS today, slashing onboarding friction and reducing support overhead. This hands-on tutorial shows exactly how to wire up Google OAuth 2.0 in a .NET app — complete with code, security notes, and the context every SaaS team needs in 2026.
Why Implement Social Login?
- Users (especially enterprise) avoid new passwords; login with Google, GitHub, or Microsoft shortens the funnel
- Reduces credential support and forgotten password tickets
- Outsources security and SSO to a trusted provider, benefiting small teams with enterprise-grade auth
1. Register Your App in the Google API Console
- Go to the Google API Console
- Create a new project, enable the "Google+ API", and configure the OAuth consent screen (add your SaaS name, support email, etc.)
- Add authorized redirect URIs (e.g.,
https://yourapp.com/signin-google)
2. Add Client ID and Secret to Your Configuration
Store Google credentials in your app’s config (never hard-coded!). In appsettings.json or your config system:
"Authentication": {
"Google": {
"ClientId": "your-google-client-id",
"ClientSecret": "your-google-client-secret"
}
}
3. Install and Configure the Authentication Middleware
In your Blazor or ASP.NET Core app, add the NuGet package Microsoft.AspNetCore.Authentication.Google, then include middleware in your startup code:
// Startup.cs or Program.cs
services.AddAuthentication(options => {
options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
})
.AddCookie()
.AddGoogle(options => {
options.ClientId = Configuration["Authentication:Google:ClientId"];
options.ClientSecret = Configuration["Authentication:Google:ClientSecret"];
});
4. Update the Login UI
Add a "Sign in with Google" button to your login page:
<a class="btn btn-google" href="/signin-google">Sign in with Google</a>
Handle redirection and post-login callbacks securely (validate all state, reject suspect tokens).
5. Account Linking & Security Guidance
- For users who previously signed up with email/password, offer to link their account on first Google login (avoid doppelganger accounts)
- Store only the minimum user info (name, email, ID tokens), never passwords or excessive profile data
- Allow users to disconnect their Google account and revoke access
- Regularly review and rotate OAuth credentials
Checklist for Secure Google OAuth in .NET SaaS
- Register app and consent screen with accurate brand info
- Store client credentials outside source code
- Update login UI and support OAuth redirect flows
- Handle account linking to avoid duplicate users
- Test all edge cases: denied consent, revoked permission, auth token expiry
- Audit user data access and privacy settings
Extra: Speed Up Implementation with DevKit
Using CodeBlock DevKit or a similar boilerplate? Social login flows (Google, GitHub, Microsoft) are included, with extensible UI components and best-practice auth handling out of the box. Ideal for .NET SaaS teams focused on domain features, not auth plumbing.