Logging into apps has come a long way. Not too long ago, pretty much every website or app had its own login screen, and you had to remember a different password for each one. It was messy, annoying, and honestly not very safe. That’s why modern apps have shifted toward smarter, easier, and more secure ways to handle logins — and that’s where protocols like OpenID Connect (OIDC) come in.

If you’ve ever logged into a website using your Google or Microsoft account, you’ve already seen OIDC in action. It quietly works behind the scenes to handle the complicated stuff — making sure you’re who you say you are — while giving you a smooth, hassle-free login experience.

In this blog, we’ll unpack what OIDC is, how it works, and why it matters. No jargon. No complicated technical lectures. Just clear, simple explanations that actually make sense.

Ready? Let’s dive in.

What is OpenID Connect (OIDC)?

Alright — so what exactly is OpenID Connect, and why do people keep bringing it up when they talk about modern logins?

Think of OIDC as a helpful add-on to something called OAuth 2.0. Now, OAuth 2.0 is a popular system apps use to get permission to access your data without needing your password. It’s great for things like letting a photo editing app access your Instagram photos or a calendar tool peek into your Google Calendar.

But here’s the thing: OAuth wasn’t really built to figure out who you are. It just handles access. That’s where OpenID Connect (OIDC) steps in.

OIDC is like an identity badge that sits on top of OAuth 2.0. It helps apps not only get permission to access stuff but also verify who’s actually logging in. So when you hit that “Sign in with Google” button, it’s OIDC making sure your identity checks out before giving the app a thumbs-up.

The best part? It works across websites, mobile apps, and APIs. So whether you’re using a browser on your laptop, an app on your phone, or a smart device on your desk, OIDC’s got your back — making sure logins stay simple and secure.

How OpenID Connect Works

Okay, so now that we know what OIDC is, let’s talk about how it actually works. Don’t worry — I’ll keep this simple and skip the overcomplicated tech speak.

Imagine you’re trying to log into an app. Instead of making you create a new account and password, the app says, “Hey, wanna just log in with your Google account?” You click yes. Here’s what happens behind the curtain:

1. The app sends you to Google (or whatever identity provider you picked) and says, “Can you check who this person is for me?”
   
2. You log into Google, and it makes sure everything looks good — maybe asks for your password or does a face scan or whatever you’ve set up.
3. If you’re verified, Google creates a little digital note called an ID token. This token basically says, “Yep, this person is who they claim to be.”
   
4. Google sends that token back to the app you were trying to use.
5. The app looks at that token and says, “Cool, everything matches. Come on in.”
   

It’s kinda like going to a club where the bouncer (the app) asks a trusted friend (Google) if you’re legit. If your friend vouches for you, you’re in.

The cool part is — you never have to hand your password to the app itself. The app just trusts the ID token coming from Google or whichever provider you chose. That’s why logins through services like “Sign in with Google” feel so easy and safe.

And that’s the basic idea behind how OpenID Connect works. It’s fast, clean, and lets you skip making a million usernames and passwords you’ll forget anyway.

OIDC vs OAuth 2.0: What’s the Difference?

People often mix up OIDC and OAuth 2.0 because they work together, but they actually handle two different jobs. Let’s clear this up once and for all.

OAuth 2.0 is all about permissions. It helps apps get access to stuff you’ve approved — like your email inbox, photo gallery, or calendar — without needing your password. But here’s the catch: OAuth doesn’t actually prove who you are. It just says, “This person has permission to do this thing.”

OpenID Connect (OIDC), on the other hand, is all about identity. It takes that OAuth system and adds a way for apps to confirm who’s on the other side of the screen. So when you log in with your Google or Microsoft account, it’s OIDC making sure it’s really you and not someone pretending.

Here’s a super simple way to think about it:

• OAuth 2.0: “Can this person access this stuff?”
  
• OIDC: “Who is this person?”
  

The reason they get mixed up is because OIDC is built on top of OAuth 2.0. It uses the same kind of behind-the-scenes handshake but adds a special ID Token that carries your verified identity info.

So while OAuth 2.0 might let an app access your calendar, OIDC will first confirm you’re actually you before handing over those permissions.

That’s why you’ll see them together in most modern apps, working side by side like the perfect tag team.

Key Components of OpenID Connect

Alright, now that we know what OIDC does and how it works, let’s meet the main pieces that make it all happen. These are the little parts working behind the scenes every time you log in with something like “Sign in with Google.”

ID Token

This one’s the MVP. The ID Token is a little digital card (in JSON Web Token — or JWT — format) that says who you are. It might have stuff like your name, email address, profile picture, and a few other bits depending on what the app asked for. The app reads this token to know, “Yep, it’s you.”

Access Token

While the ID Token proves your identity, the Access Token lets the app request stuff on your behalf — like reading your calendar or contacts. It’s not about who you are, it’s about what you’re allowed to do.

Refresh Token

This is a handy little backup. Some tokens expire quickly (for security reasons), and when they do, the Refresh Token can grab a fresh new Access Token without making you log in again. It keeps your session going without bothering you.

Discovery Document

Sounds fancy, but it’s just a JSON file living at a known URL (usually /.well-known/openid-configuration). It tells the app where to send login requests, where to get tokens, and where to find public keys to verify tokens. It’s like a map for the app to follow.

 UserInfo Endpoint

Once you’re logged in, if the app wants extra info about you (like your display name or profile pic) that wasn’t in the ID Token, it can call this UserInfo Endpoint. Think of it as a contact card the app can ask for, with your permission.

And that’s the crew behind every OIDC login. Each one plays its part to keep things running smoothly, safely, and without a bunch of passwords floating around.

Common OpenID Connect Flows (with PKCE connection)

Alright — time to talk about the different ways apps can use OIDC to handle logins. These different methods are called flows, and which one an app uses depends on what kind of app it is and how it needs to handle security.

Let’s break down the big ones you’ll run into:

Authorization Code Flow (with PKCE)

This is the go-to for most modern apps, especially web and mobile apps. Here’s how it works:

• The app sends you to the login page (like Google or Microsoft)
• You log in
• The identity provider sends an authorization code back to the app
• The app swaps that code for tokens (ID token + Access token)

PKCE (pronounced “pixie”) is a security upgrade for this flow, especially for mobile and browser apps, to prevent sneaky attacks.

Implicit Flow

This one was popular back in the day for single-page apps (SPAs), but it’s kind of outdated now because it sends tokens directly through your browser, which isn’t super safe anymore. Most developers avoid this now in favor of safer options like Authorization Code Flow with PKCE.

Hybrid Flow

This is like a mashup of the other two. It’s flexible and lets the app get some tokens straight away while still following the authorization code process for others. Not super common for everyday apps, but handy in certain advanced setups.

Want a deeper dive into how PKCE works and why it’s important? Check out our guide here.

Section 8: Security Considerations with OIDC (with blog link)

Use PKCE with Authorization Code Flow
We mentioned PKCE earlier, but it’s worth repeating — if your app’s using the Authorization Code Flow, PKCE is non-negotiable these days. It prevents attackers from stealing authorization codes and swapping them for tokens.

If you’re curious how it works under the hood or how to add it to your setup, we’ve written a full, beginner-friendly breakdown you can check out right here.

Popular OpenID Connect Providers

Alright — so who actually provides these OIDC logins you see everywhere? Tons of big-name services and platforms support OpenID Connect these days. Some you’ve probably used without even realizing it.

Here’s a quick rundown of the most popular ones:

1. Okta

A popular identity provider for businesses, especially for apps that need enterprise-grade single sign-on and security controls

2. SSOJet

A newer player in the identity space, offering developer-friendly authentication tools with OIDC baked in.

And honestly, there are dozens more. The beauty of OIDC is that it’s an open standard, so any provider can support it — and many do.

3. Google

Probably the one you’ve seen the most. That “Sign in with Google” button on apps and websites? Yep — that’s OIDC doing its thing.

4. Microsoft

If you use a Microsoft account for Outlook, Xbox, Teams, or Azure, you’ve used OIDC. It’s also a go-to for enterprise single sign-on setups.

5. Apple

Apple’s “Sign in with Apple” feature is built on OIDC too, with a few extra privacy tweaks like hiding your actual email address if you want.

Conclusion

And there you have it — OpenID Connect, explained without the boring, overcomplicated tech talk.

At its heart, OIDC is all about making logins easier, safer, and smarter. It takes the solid permission system of OAuth 2.0 and adds a layer of identity on top, so apps don’t just ask “Can this person access this stuff?” — they also know “Who is this person?”

Whether you’re logging into an app with your Google account, using single sign-on at work, or building your own product that needs user authentication, OIDC is likely working behind the scenes to keep things secure and hassle-free.

The best part? It’s built to work across web apps, mobile apps, APIs, and even modern passwordless setups. So no matter what the future of logins looks like, OIDC’s already ready for it.

If you’ve made it this far — nice work! Hopefully, you’ve got a solid grip on what OpenID Connect is, how it works, and why it matters.

*** This is a Security Bloggers Network syndicated blog from SSOJet authored by Vijay Singh. Read the original post at: https://ssojet.com/blog/openid-connect-explained/