Session Tokens vs Cookies: What's Right for Your Web App?

When building a web application, one of the most important decisions you'll make is how to manage user sessions. Two common methods are using session tokens and cookies. But which one is right for your app? In this article, we'll dive into the pros and cons of both methods to help you make an informed decision.

What are Cookies?

Cookies are small text files stored on the user's browser when they visit a website. They can store a variety of information, but they're often used for authentication and session management. When a user logs in, the server can set a cookie with a session ID, and the browser will automatically send that cookie with every subsequent request to the server.

There are a few different types of cookies, but for session management, the most important are HttpOnly cookies. These cookies can only be accessed by the server, not JavaScript running in the browser, which helps protect against certain types of attacks.

There are a couple other cookie flags that are important for security:

• The Secure flag, which tells the browser to only send the cookie over HTTPS.
• The SameSite flag, which controls when the browser sends the cookie with cross-site requests.

What are Session Tokens?

Session tokens, on the other hand, are often used in Single Page Applications (SPAs). Instead of storing the session ID in a cookie, the server sends a token (often a Json Web Token, or JWT) to the client, which then stores it in localStorage or sessionStorage. Whenever the client makes a request to the server, it includes the token in the Authorization header.

Token Storage

Storing tokens in localStorage or sessionStorage has some advantages. It allows the client to access the session data, which can be useful for displaying user information or adjusting the UI based on the user's permissions. And since the token is sent manually with each request, the client has more control over when and how it's sent.

But token storage also comes with some security risks. If an attacker can run JavaScript on your site (a Cross-Site Scripting, or XSS, attack), they can steal the user's token and use it to impersonate them.

Security Risks: XSS vs CSRF

Both cookies and session tokens have their own security risks.

As mentioned before, session tokens are vulnerable to XSS attacks. If an attacker can inject malicious JavaScript into your site, they can steal the user's token and use it to make requests to the server as if they were the user.

Cookies, on the other hand, are vulnerable to Cross-Site Request Forgery (CSRF) attacks. In a CSRF attack, an attacker tricks the user into making a request to your site from another site. Since the browser automatically includes cookies with every request, the attacker can make requests on the user's behalf without their knowledge.

HttpOnly cookies can help protect against both of these attacks. Since they can't be accessed by JavaScript, they're safe from XSS attacks. And the SameSite flag can help prevent CSRF attacks by controlling when the cookie is sent with cross-site requests.

When to Use One Over the Other

So when should you use session tokens, and when should you use cookies?

If you're building a traditional web app, where the server renders the HTML for each page, cookies are often the best choice. They're simple to use, and with HttpOnly and SameSite flags, they can be quite secure.

If you're building a SPA, or a mobile app, session tokens might be a better choice. They give the client more control over when and how the token is sent, and they allow the client to access the session data.

However, it's important to be aware of the security risks of storing tokens in localStorage or sessionStorage. If you choose to use session tokens, make sure to put measures in place to protect against XSS attacks.

Real-world Guidance

In the real world, the choice between session tokens and cookies isn't always clear-cut. It often depends on the specific needs of your app and your team's expertise.

If you're using a service like Authava, you might not have to worry about this decision at all. Authava handles session management for you, so you can focus on building your app.

In the end, the most important thing is to understand the pros and cons of each method, and to make an informed decision based on your app’s needs. Whether you choose session tokens or cookies, make sure to prioritize security and user experience.

Remember, the goal of session management is not just to keep track of the user's session, but to do so in a way that's secure, efficient, and seamless for the user.