This question comes up in every code review, every architecture discussion, and every time someone starts a new project. JWT or sessions? Which one is better?
The annoying answer is: it depends. But that's not helpful, so let me actually break down when each one makes sense. I've built apps with both, debugged issues with both, and scaled both to millions of users. Here's what I've learned.
How Sessions Actually Work
Sessions have been around forever. When a user logs in, your server creates a session ID—just a random string—and stores information about that user in a database or memory cache (like Redis).
The server sends that session ID to the user's browser, usually in a cookie. Every time the user makes a request, the cookie gets sent back. Your server looks up that session ID, finds the user's data, and boom—you know who they are.
Here's what happens step by step:
- User logs in with username and password
- Server checks credentials, creates a session ID
- Server stores session data in Redis/database
- Server sends session ID to browser in a cookie
- Browser automatically includes cookie in future requests
- Server looks up session ID to identify the user
It's simple and it works. The session data lives on your server, and the user just holds a key to access it.
How JWT Works (Quick Recap)
JWT is different. When a user logs in, your server creates a token that contains the user's information right inside it. The server signs this token with a secret key, then sends it to the user.
The user stores this token (usually in localStorage or a cookie) and sends it back with every request. Your server checks the signature to make sure it's legit, then reads the user data directly from the token. No database lookup needed.
JWT flow looks like this:
- User logs in with username and password
- Server checks credentials, creates a JWT with user data
- Server signs the JWT with its secret key
- Server sends JWT to the browser
- Browser stores JWT and sends it with future requests
- Server verifies signature and reads user data from token
The key difference? With JWT, all the data is in the token itself. Your server doesn't need to remember anything.
The Big Comparison Table
Let's get into the actual differences that matter when you're building something:
| Feature | Sessions | JWT |
|---|---|---|
| Server Storage | Needs Redis/DB | Nothing stored |
| Scalability | Harder (shared storage) | Easier (stateless) |
| Token Size | Small (just an ID) | Larger (contains data) |
| Logout | Easy (delete session) | Hard (token stays valid) |
| Revocation | Instant | Wait for expiry or use blacklist |
| Performance | DB lookup each request | Just verify signature |
| Mobile Apps | Can be annoying | Works perfectly |
| Multiple Servers | Need shared storage | Works anywhere |
When Sessions Make More Sense
Sessions aren't old and busted. They're actually the right choice for a lot of apps. Here's when I reach for sessions:
Traditional Server-Rendered Apps
If you're building a classic web app where the server renders HTML pages (like with Rails, Django, Laravel, Express with templates), sessions just work. Your framework probably has session management built in. Why complicate things?
When You Need Instant Logout
This is huge. With sessions, when a user clicks logout, you delete their session and they're immediately logged out everywhere. Done.
With JWT, the token stays valid until it expires. Even if they click logout, if someone has their token, it still works. You can work around this with blacklists, but now you're basically recreating sessions with extra steps.
Small to Medium Apps
If you're not running hundreds of servers, the "sessions don't scale" argument doesn't really matter. One Redis instance can handle sessions for millions of users. Don't overcomplicate your app solving problems you don't have.
When You Need to Store Lots of Data
Sessions can store whatever you want—shopping carts, form data, preferences, whatever. With JWT, every byte you add makes the token bigger, and you're sending that back and forth with every request.
💡 Real Talk: I've seen people use JWT just because it seemed cool or modern, then spend weeks building workarounds for logout and revocation. If sessions work for your use case, use sessions.
When JWT Makes More Sense
Okay, but JWT isn't pointless. There are definitely times when it's the better choice:
APIs for Mobile Apps
Mobile apps and JWT are a perfect match. The app stores the token locally, includes it in API requests, and everything just works. No cookies, no session management hassles.
Microservices
If you have multiple services that all need to know who the user is, JWT is way easier. Pass the token to any service, they all verify it with the same secret key, and they can all read the user info. No shared session storage needed.
Single Page Applications (SPAs)
React, Vue, Angular apps usually work better with JWT. The frontend handles storing and sending the token, and your backend is just a stateless API. Clean separation.
When You're Already Running Multiple Servers
If you're at the scale where you have load balancers and multiple server instances, JWT means you don't need to set up Redis clusters or sticky sessions. Any server can handle any request.
Third-Party API Access
If you're building an API that external developers will use, JWT is the standard. OAuth 2.0 uses JWTs, and developers expect them.
The Hybrid Approach (What I Usually Do)
Here's a secret: you don't have to pick just one. I usually use both in the same app.
Short-lived JWT for access + Long-lived session for refresh
Give users a JWT that expires in 15 minutes. Also give them a refresh token (stored in the database like a session) that lasts weeks. When the JWT expires, they use the refresh token to get a new one.
This gives you the benefits of both:
- Most requests use stateless JWT (fast, scalable)
- Refresh tokens let you revoke access instantly
- Short JWT expiry limits damage from stolen tokens
- You can log users out properly
Yeah, it's more complex. But it's the best of both worlds for apps that need serious security.
Performance: Does It Actually Matter?
People talk about JWT being faster because there's no database lookup. In practice? The difference is tiny.
Looking up a session ID in Redis takes maybe 1 millisecond. Verifying a JWT signature takes maybe 0.1 milliseconds. Sure, JWT is technically faster, but if your app is slow, sessions aren't the problem.
Where it does matter is at huge scale. If you're processing millions of requests per second, those milliseconds add up. But if you're at that scale, you probably have engineers who can help you figure this out.
Security: Which Is More Secure?
Neither is inherently more secure. Both can be done right or done wrong.
Session security concerns:
- Session fixation attacks if not handled properly
- CSRF attacks if you're not careful with cookies
- Session storage could be compromised
JWT security concerns:
- Stolen tokens work until expiry
- Secret key compromise is catastrophic
- XSS attacks can steal tokens from localStorage
- Can't revoke tokens without extra work
Both require you to know what you're doing. Sessions have decades of battle-testing. JWT is newer and people make more mistakes with it. But done right, both are fine.
Implementation Complexity
Sessions are simpler to get started with. Most frameworks handle them automatically. You basically just say "start a session" and you're done.
JWT requires more work. You need to:
- Generate and store a strong secret key
- Create tokens on login
- Send tokens to the client properly
- Verify tokens on every protected route
- Handle expired tokens
- Implement refresh token logic (probably)
- Figure out logout (which is annoying)
Not impossible, but definitely more moving parts.
My Actual Recommendation
After building dozens of apps with both approaches, here's what I do:
Use sessions if:
- You're building a traditional web app
- You're a small team or solo developer
- You need instant logout/revocation
- You're storing lots of user data between requests
- Your framework makes sessions dead simple
Use JWT if:
- You're building a mobile app API
- You have microservices
- You're building a SPA (React, Vue, Angular)
- You're running lots of servers
- You need to give API access to third parties
Use both (hybrid) if:
- Security is critical (banking, healthcare, etc.)
- You need both performance and control
- You're willing to handle the extra complexity
Common Myths I'm Tired of Hearing
Myth: "Sessions don't scale"
Nonsense. Redis can handle millions of sessions. If you're not Facebook, you'll be fine.
Myth: "JWT is more modern and better"
JWT is newer, but that doesn't make it better. Sessions work great for most apps.
Myth: "You have to pick one"
You can use both. Many big apps do exactly that.
Myth: "JWT is stateless so it's always faster"
If you implement refresh tokens and blacklists, you're doing database lookups anyway. Now you've got all the complexity of JWT plus state.
The Bottom Line
Don't pick JWT just because it sounds cool. Don't stick with sessions because it's what you know. Think about what you're actually building.
Building a simple web app? Sessions are fine. Building an API for mobile apps? JWT makes sense. Building something huge with complex requirements? You'll probably end up using both.
And honestly? For most projects, either one will work just fine. The choice matters way less than getting the implementation right. Bad JWT is worse than good sessions, and vice versa.
Pick what makes sense for your project, implement it securely, and move on to building features that actually matter to your users.