How Apps Really Check Who You Are
So, here’s a thought. Ever opened your email on your phone and wondered why it works only for you, not for someone else’s account? That’s not random. That’s because of something called API authentication.
Every single time you open an app bank, maps, chat there’s an API quietly doing the work. But before it hands over any info, it needs to make sure you’re the right person. Otherwise… anyone could walk in, grab data, or even mess things up. Imagine if someone could just take money from a bank by hitting the right link. Crazy, right? That’s why these checks exist.
Now, there are a bunch of ways to do it, but three are super common. API Keys. JWT. And OAuth. Each one’s like a different style of ID check.
API authentication with API Keys
API Keys
Think of it like a secret pass. You flash it, you get in. That’s pretty much it.
It’s just a long weird-looking string of letters and numbers. The app sends it to the server. If it matches, cool—you’re allowed in.
Sometimes it’s added in the URL, but that’s kind of risky because it can show up in history. The safer way is to tuck it in headers.
Keys are simple. Good when you don’t care about personal stuff. Like weather apps, stock updates, or small internal tools. But if private data’s involved, you probably don’t want to rely on just that.
API authentication with JWT
JWT
Okay, picture this. You’re at a concert. Instead of showing ID every time, you get a wristband once and just walk around freely. That’s exactly what a JWT is doing.
JWT stands for JSON Web Token. It’s like a little packet that carries info about you. Not just a password, but stuff like your ID, role, and when it should expire.
It’s split into three bits: header, payload, signature. The signature makes sure no one’s been messing with it.
Here’s how it goes: you log in, the server checks your details, gives you a token. Your browser or app keeps it. Then every time you ask for something the token goes with the request. The server just checks the token instead of asking for your password again.
This is why apps can let you log in once and move around easily without constant re-checks. Works great for big apps where loads of users are active at the same time.
API authentication with OAuth
OAuth
You’ve definitely seen this. “Log in with Google” or “Log in with Facebook.” That’s OAuth in action.
Instead of giving your password to every random app, OAuth says, “Hey, I’ll let Google handle it. You just give permission.”
So the flow goes like this. You click log in with Google. You get sent to Google’s page. It asks if you’re okay with sharing, say, your email. You hit yes. Google gives the app a code. The app swaps that code for a token. That token lets the app grab the data you allowed—nothing more.
Super handy when apps need to connect with others. Think Twitter apps that schedule posts or services that need your GitHub repos.
| Method | Best for | Pros | Cons |
|---|---|---|---|
| API Keys | Simple server to server or public APIs | Easy to use, trackable | No expiry by default, limited access control |
| JWT | Stateless user sessions for web and mobile apps | Scalable and fast, self-contained | Requires secure storage, revocation can be tricky |
| OAuth | Third-party logins and delegated access | No password sharing, limited scoped access | More complex flow, requires provider integration |
Which API authentication is Right
Which One’s Right
Well, it depends.
Keys are fine for small stuff, nothing too private.
JWTs are awesome when you want things fast and scalable.
OAuth shines when you need sign-ins from other accounts or outside apps.
None of them is “best” all the time. It’s more like, pick the one that fits what you’re building and how much security you actually need.
