Player Authentication in Unity: The Complete Guide

Almost every Unity game reaches the same wall. You want to save progress to the cloud, show a leaderboard, sell something, or just greet a returning player by name — and to do any of that, you first have to know who the player is. That's player authentication, and this guide is the map: the real ways to do it in Unity, what tends to break, and where each provider hides its surprises.

It's written for the small-studio reality. No dedicated backend engineer, no appetite for babysitting an auth server, and no patience for a login button that takes three weeks. If that's you, start here and follow the links out to the provider you actually need.

The three ways to authenticate players in Unity

There are really only three shapes this takes, and they trade off the same way every time.

Roll your own email and password. You build a sign-up form, store password hashes, write a "forgot password" flow, and run a server to hold all of it. It works, and it's fully under your control. It also makes you the party responsible when credentials leak, and it's the option players are least excited to use — every extra field on a sign-up form costs you completions.

Wire up each provider's native SDK. Google's plugin, the Facebook SDK, a Steamworks wrapper. Each one is a separate integration, often with per-platform native code, and they age badly — an SDK that worked last year wants a new Gradle version and a different manifest entry this year. For a login button, that's a lot of surface area to maintain.

Use a hosted OAuth / SSO service. The provider becomes configuration instead of code. The OAuth exchange — the part that needs a client secret and a real web redirect — runs on someone else's server, and your game receives the finished player identity. This is the path Oathwall takes, and it's why adding a second provider is a one-string change instead of a second integration.

If you're new to the vocabulary here, what single sign-on means for a game is a five-minute read that makes the rest of this page click.

What actually makes Unity authentication hard

The button is never the problem. Three things underneath it are.

A client secret can't live in your build

Most OAuth providers hand you a client ID and a client secret. The secret is meant for a confidential server. Drop it into a Unity MonoBehaviour and it ships inside your build — and pulling readable strings out of an .apk takes about a minute with off-the-shelf tools. Once a secret is in a shipped binary, it's public, and rotating it means a new release. Shipping OAuth client secrets in a game build is a genuine security mistake, not a style preference.

Redirect URIs and deep links

OAuth was designed around web redirects. A game isn't a website. So after the player taps "Allow," the provider needs a way back into your running game — which means registering a custom URI scheme and handling a deep link on both Android and iOS. Get the redirect URI wrong by a single character and the provider returns redirect_uri_mismatch before login even starts. It's the most common reason an integration "just doesn't work."

Every provider behaves differently

This is the part that surprises people. The providers aren't interchangeable:

Provider	Protocol	Returns email?	The catch
Google	OAuth 2.0 (OIDC)	Yes	Unverified-app warning screen during testing
Sign in with Apple	OAuth 2.0 (OIDC)	Yes (or a relay)	Name only on first login; mandatory on iOS
Steam	OpenID 2.0	Never	No email, no password, PC-centric
Facebook	OAuth 2.0	Yes, with review	email scope needs App Review for production
Discord	OAuth 2.0	Sometimes	Email may be unverified
GitHub	OAuth 2.0	Often hidden	Public email is frequently private → null
Epic Games	OAuth 2.0 + PKCE	Sometimes	PKCE is mandatory; no avatar
Twitch	OAuth 2.0	With one scope	Needs user:read:email; display names change
X (Twitter)	OAuth 1.0a	With a setting	Email needs a portal toggle enabled
Microsoft / Xbox	OAuth 2.0 (OIDC)	Usually	Work/guest accounts return a UPN, not an inbox

Design your account system around "every provider gives me an email" and Steam breaks it on day one. These differences are exactly where the integration work hides, and they're covered per-provider in the guides below.

The Oathwall approach

Oathwall keeps the confidential half of OAuth on its own servers. Your provider secrets live in the dashboard, the token exchange happens server-side, and your game receives the result. On the Unity side, the whole client integration is one class:

using PixitGames.SSOLoginKit;

public class LoginManager : SsoClientBase
{
    // Hook to a UI button. Opens the hosted sign-in
    // in the system browser and deep-links back for you.
    public void OnLoginButton() => StartLogin("google");

    protected override void OnLoginSuccess(LoginResult user)
    {
        Debug.Log($"Welcome, {user.name}!");
        // user.id · user.email · user.provider
    }
}

Switching providers is the string: StartLogin("apple"), StartLogin("steam"). The SDK opens the system browser, handles the deep link back into the game, and stores and refreshes the session tokens for you. It also ships SilentLogin() to resume a saved session on the next launch, and CreateProviderButtons() to build the login screen from whichever providers you enabled in the dashboard. The only identifier your build carries is a public appKey — safe to expose, useless without the secret behind it.

Choose your provider

Each guide follows the same shape: the specific pain, the setup, the real C#, and the provider's own gotcha.

• Google Sign-In in Unity — the most-requested one. Gives you a verified email; watch the "app isn't verified" screen while you're still in testing.
• Sign in with Apple in Unity — required on iOS if you offer any other social login. The player's name arrives only on the very first authorization, so you have to capture it then.
• Steam Login in Unity — the sign-in PC players expect. OpenID, not OAuth, and it never returns an email.
• Facebook Login in Unity — no Facebook SDK in your project. The email permission needs Meta's App Review before it works for the public.
• Discord Login in Unity — a natural fit for community-driven and multiplayer games. Its email can come back unverified, so check before you trust it.
• GitHub Login in Unity — for dev tools, game jams, and modding hubs. GitHub users often keep their email private, so it can come back null.
• Epic Games Login in Unity — for Epic Games Store titles and EOS cross-play. Uses OAuth with mandatory PKCE, handled for you.
• Twitch Login in Unity — for stream-integrated games and Twitch communities. The email hinges on a single scope.
• X (Twitter) Login in Unity — for social and community games. The email only appears if a developer-portal setting is enabled.
• Microsoft & Xbox Login in Unity — one identity for Windows and Xbox players. Work and guest accounts return a UPN rather than a real inbox.

Solve a specific problem

If you landed here from a more specific question, these go straight at it:

• How to Add Login to Your Unity Game — the start-to-finish walk-through, including how to test the whole flow in a browser before you build.
• Authentication in Unity Without a Backend — what a server normally does for auth, and how to ship login without running one.
• Never Ship OAuth Client Secrets in Your Unity Build — why a secret in your build is public the day you ship, and where it belongs instead.
• Cross-Platform Login in Unity — one login manager across iOS, Android, desktop, and WebGL, and the per-platform gotchas.

Beyond Unity

Unity gets the packaged SDK, but Oathwall's login is a plain HTTP flow — so it works from any engine that can open a URL and make requests.

• OAuth Login Without an SDK — the full REST and deep-link contract behind the SDK, endpoint by endpoint. Wire it into any engine yourself.
• Godot OAuth Login — the same flow as real GDScript, with HTTPRequest and OS.shell_open, and an honest look at the deep-link part Godot leaves to you.

Learn the concepts

If you'd rather understand the machinery before wiring it up:

• What Is SSO? — single sign-on in plain terms.
• OAuth 2.0 Explained for Game Developers — the flow behind every "Sign in with…" button.
• What Is PKCE — the extension that makes OAuth safe for clients that can't keep a secret.
• Access vs. Refresh Tokens — what your game actually gets back, and how sessions stay alive.
• id_token vs access_token — which token proves identity and which one authorizes calls.
• What Is a Redirect URI — the return address OAuth insists on, and the one value to register with Oathwall.
• Deep Linking in Unity — how the login result gets back into your running game on iOS and Android.
• Storing Auth Tokens in Unity — why not PlayerPrefs, and where the refresh token actually belongs.
• Session Management for Games — staying signed in across launches and devices, and revoking on demand.

Compare your options

Oathwall isn't the only way to add player login — and it isn't right for every project. Honest comparisons against the common alternatives:

• Oathwall vs PlayFab — a focused login versus a full LiveOps backend. Which you need depends on how much backend you want to run.
• Oathwall vs Firebase Auth — game-first providers (Steam, Discord) and a lighter SDK versus a mature, general-purpose service.
• Oathwall vs Unity Gaming Services — independent and portable versus tightly integrated with the UGS backend.
• Oathwall vs Auth0 — game login versus an enterprise identity platform.

Get started

Oathwall's free plan covers development — one app and ten users — which is enough to build and test the entire flow before you ship. When you're ready, it's available on the Unity Asset Store.