Session Cookies: From Basics to Best Practices

At a glance

• Session cookies are temporary files that manage essential website functions like login status and shopping carts, automatically deleting when users close their browsers.
• While session cookies don't require explicit consent under GDPR, as they're necessary for website operations, businesses still need proper security measures to prevent hijacking and unauthorized access.
• Organizations can use tools like Transcend Consent Management to ensure transparency, privacy protection, and effective management of session cookies.

Understanding session cookies

Session cookies are temporary files that websites use to store user information during a single browser session, such as maintaining login status, remembering shopping cart items, and preserving preferences across pages.

Unlike persistent cookies, session cookies are automatically deleted when the user closes their browser, making them more privacy-friendly and often exempt from strict consent requirements under regulations like GDPR.

While there are several types of cookies, each serving different purposes, this article focuses on session cookies - a fundamental component of modern web browsing.

Purpose of session cookies and session cookies examples

Session cookies serve several critical functions that significantly improve user experience and website functionality:

1. User authentication: They keep you logged in as you move from one page to a new page on a website.
2. Shopping carts: Session cookies remember shopping cart information as users browse different product pages.
3. Form data retention: If you're filling out a multi-page form, session cookies can save your progress between pages.
4. Personalization: Cookies can remember your preferences (like language settings) for the duration of your visit.
5. Analytics: Session cookies help websites understand user behavior within a single visit.
6. Security: They can be used to prevent certain types of attacks, like cross-site request forgery (CSRF).

Though a cookieless future is a very real possibility, cookies can have a positive impact on user experience, so long as they're handled according to data privacy best practices.

How session cookies differ from persistent cookies

The key difference between session and persistent cookies (sometimes called tracking cookies) is their lifespan. Session cookies work only during active browsing and disappear when the user's browser window is closed. Persistent cookies remain on a user’s devices for weeks, months, or even years.

Common uses of persistent cookies include:

Login convenience

• Keeping you signed in to Gmail across browser restarts
• Remembering your Netflix profile selection
• Saving your Spotify account preferences

Site personalization

• Maintaining your Amazon shopping preferences
• Keeping your preferred language on Wikipedia
• Saving your dark mode setting on social media

User analytics

• Tracking return visits to improve site features
• Measuring how often you use certain functions
• Understanding which content brings you back

Session cookies prioritize immediate needs and temporary data, while persistent cookies create a smoother experience across multiple visits.

Since session cookies disappear after use, they typically pose lower security risks than persistent cookies, which store data longer.

How do session cookies work?

Session cookies operate through a simple yet effective process on a user's computer or mobile device:

1. When a user session begins on a website, the server creates a unique, randomly generated "session ID."
2. This session ID is stored in a server-specific cookie on their browser.
3. As they navigate through different web pages on the site, your browser sends this session ID with each new request.
4. The server uses this ID to retrieve your session data, allowing it to remember your actions and preferences.
5. When you close your browser or log out, the user session ends and the cookie is deleted.

This server-specific nature of session cookies means they cannot be accessed or used by any other website or server, enhancing security and privacy.

Security and privacy considerations

Session cookies play a key role in web security on a user's computer or mobile device. They help keep user data safe and prevent unauthorized access. But they can also be targets for attacks if not handled correctly.

While session cookies are generally considered low-risk from a privacy perspective, there are still important security considerations:

1. Session hijacking: If an attacker intercepts a session cookie, they could potentially impersonate the user. To mitigate this:
   • Use HTTPS to encrypt all communication
   • Implement secure cookie flags (HttpOnly and Secure)
   • Regularly regenerate session IDs after a user logs in
2. Cross-site scripting (XSS): Malicious scripts could potentially access session cookies. Implementing the HttpOnly flag prevents JavaScript from accessing the cookie.
3. Session fixation: An attacker might try to set a known session ID. To prevent this, always generate a new session ID after user authentication and upon session renewal to prevent attackers from using a known session ID.
4. Logout procedures: Ensure that sessions are properly terminated when a user logs out.

Session hijacking risks

Session hijacking is a major threat to cookie security. Attackers try to steal or guess session IDs to take over user accounts. This can happen through network eavesdropping or cross-site scripting (XSS) attacks.

To guard against hijacking:

• Use HTTPS to encrypt all traffic
• Set short expiration times for session cookies
• Regenerate session IDs after login
• Validate IP addresses and user agents

These steps make it harder for attackers to capture or use stolen data.

Cross-site request forgery (CSRF)

CSRF attacks trick users into making unwanted actions on a site they're logged into. The attacker uses the victim's active session cookie to perform actions without their knowledge.

To prevent CSRF:

• Use anti-CSRF tokens in forms
• Check the Origin and Referer headers
• Implement the SameSite cookie attribute

These methods help ensure requests come from legitimate sources and not malicious sites.

Best practices in securing session cookies

To keep session cookies safe, web developers should follow these best practices:

1. Use the HttpOnly flag to prevent JavaScript access to cookies
2. Set the Secure flag to only send cookies over HTTPS
3. Use strong, random session IDs
4. Implement proper logout mechanisms
5. Monitor for suspicious activity

It's also important to keep cookies small and only store necessary data. This reduces the impact if a cookie is compromised. Regular security audits can help spot weaknesses in cookie handling.

General Data Protection Regulation (GDPR) and session cookies

Under the General Data Protection Regulation (GDPR), which sets rules for handling personal data within the EU, session cookies are typically considered "strictly necessary."

This means websites must comply with GDPR when using them, but explicit user consent may not always be required for setting session cookies on a user's device.

While session cookies can be classified as personal data, the legal basis for their use is usually "legitimate interest," as they are essential for the website to function properly.

However, GDPR also gives users control over their data, requiring websites to inform users about cookie usage and offer options to manage cookie preferences, including the ability to opt out of non-essential cookies.

Third-party cookies vs session cookies

While both are types of cookies, third-party and session cookies serve very different purposes. Session cookies are set by the website you're visiting to manage basic functions—they keep you logged in, remember your shopping cart items, and save your site preferences during your visit. When you close your browser, these cookies disappear.

Third-party cookies, on the other hand, are set by external websites and stick around much longer. Their main purpose is advertising and analytics, tracking your activity across different websites to understand your interests and behaviors.

For example, if you browse running shoes on one site, third-party cookies help advertisers show you relevant ads for running gear on other sites you visit. Social media platforms also use third-party cookies to enable their "like" and "share" buttons across the web.

Transcend Consent Management helps businesses handle both types properly - ensuring session cookies support smooth site operations while giving users control over which third-party cookies can track their activity.

Controlling and blocking session cookies

Users can manage session cookies through browser settings and personal choices. This helps protect privacy and control data shared with websites.

Browser settings and cookie blocking

Most web browsers offer options to control cookies. Users can adjust these settings to block all cookies, including session cookies.

In Microsoft Edge, users can:

1. Click the menu (...)
2. Select "Settings"
3. Choose "Privacy, search, and services"
4. Scroll to "Cookies and site permissions"
5. Pick a cookie blocking option

Chrome has similar steps:

1. Click the three dots menu
2. Go to "Settings"
3. Select "Privacy and security"
4. Choose "Cookies and other site data"
5. Pick a cookie setting

These options let users block third-party cookies or all cookies. Blocking all cookies can break some websites, so users should test different settings.

User control over cookies

Users have other ways to manage cookies beyond browser settings. They can:

• Clear cookies regularly
• Use private browsing modes
• Install browser extensions for cookie control

Deleting cookies removes stored data, including login info. This can be done for specific sites or all at once. Private browsing doesn't save cookies after user sessions end.

About Transcend

The bare minimum won't cut it when it comes to earning your customers' trust. Maintaining best practices is how you create safe and seamless browsing experiences people want to return to, and it's easier with Transcend's help.

Our comprehensive suite includes must-have tools such like Privacy Center, Consent Management, and Preference Management—helping your organization maintain transparency about data collection and use, manage the full range of digital adtech, and maximize compliant customer outreach.

Get our demo today.