JWT, Authorization, Sessions: What You Read and Which to Use?

Admittedly, it is easy to feel confused when selecting the appropriate way of authentication. I have witnessed hundreds of developers lose their way on which to apply JWT, OAuth2 or conventional sessions. Then shall I dissect this into a manner that makes sense.
💬 The Real Talk:
Authentication is not universal and that is alright. Both the approaches have a different purpose and knowing the time to employ each can make you headache free in the future in matters regarding security. It is much like picking the right tool out of your toolbox – you cannot apply a hammer there and everywhere, would you?
🏛️ Traditional Sessions: The Trustworthy Classic
What it is:
Server-side authentication In this method, the user data is stored in your server and a simple cookie of the session ID is transferred to the client.
✅ When to use Sessions:

• Traditional web applications – In case you are creating a typical web application where users and interact through a browser, you have friends in sessions.
• Monolithic architectures – When your whole application runs on a single server or a tightly-knit system.
• Extreme security needs – Any application that involves sensitive data such as banking applications, healthcare applications, and any other application that is sensitive require server-side control.
• When you want to revoke immediately — Have to kick someone out? Sessions facilitate this without any strain.

⚖️ The tradeoffs:

• Needs server memory or database to save session data.
• On-demand scaling across the front-end may be difficult without shared session storage.
• Not suitable in the mobile applications or in the multi-domain cases.

🎫 JSON Web Tokens (JWT): The Stateless Performer
What it is:
Self-contained tokens that include their user information in the form of tokens. No server lookup needed.
✅ When to use JWT:

• Microservices structures – Services are able to check tokens independently of striking a central authentication server.
• Mobile apps – Ideal to use iOS and Android apps that should be able to authenticate with your API.
• Cross-domain authentication – The frontend and backend reside on different domains.
• Stateless APIs – RESTful APIs which require no shared state and which should be scaled horizontally.
• Secure and Scalable auth with refresh tokens: Save some time with short-lived auth.

⚖️ The tradeoffs:

• Before they expire, tokens cannot be invalidated (except by maintaining a blacklist, which is a defeat of the stateless intent).
• Greater size than session identities.
• Should be carefully implemented to prevent vulnerabilities to security.

🤝 OAuth2: The Delegation Expert
What it is:
A permission system (not authentication) which allows users to provide third-party applications with limited access without exchanging passwords.
✅ When to use OAuth2:

• Sign in with Google/GitHub/Facebook — users can use an existing account to sign in.
• Third-party integrations — Your app requires information to someone on their GitHub repos, Google drive, or music playlists on Spotify.
• API authorization – When making an API that is going to be integrated with.
• Multi-tenant applications – Enterprise apps where other organizations have to gain controlled access.
• Mobile applications that integrate with your API – OAuth2 with PKCE Example of secure mobile authentication.

⚖️ The tradeoffs:

• More difficult to get right.
• Needs knowledge about flows (Authorization Code, Client Credentials, etc.)
• Unnecessarily extreme internal authentication requirements.

💡 My Practical Recommendations:

• In the case of the traditional web app? → Begin with Sessions. They are proven, easier to put into effect and provide complete control.
• Developing a new SPA or a mobile application? → Choose JWT as your API, but consider revocation with grace with the use of refresh tokens.
• Social log-in or third party access required? → The only real option here is OAuth2.
• Processing really sensitive data? → Sessions that have high security levels, or JWT with extremely short expiration, and rotation of refresh tokens.

🔄 The Hybrid Routine (What Most Firms In fact do):
You do not need to decide to favor only one of them! Many production systems use:

• Social login (OAuth2 initial authentication).
• JWT to access API with limited life.
• Refresh token managing sessions.
• Refresh tokens stored on the server, revoked.

🎯 The Bottom Line:
There is no best option, it only depends on the right option in your particular case. Take into account your architecture, security needs, scalability needs, and team experience. And always keep in mind that you can always begin small and develop accordingly as you need it.