Beyond Cookies: Managing LocalStorage & IndexedDB

Date: May 25, 2026 Author: GetCookies Team Category: Technical Reading Time: 11 min

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We call them "Cookie Banners," but GDPR actually regulates "access to information stored in the terminal equipment."

That includes:

• Cookies (Old school, 4KB limit).
• LocalStorage (Persistent, 5MB+).
• SessionStorage (Tab-only).
• IndexedDB (Full database in browser).

Many "compliant" sites clear cookies when a user opts out but leave gigabytes of data in LocalStorage. This is a violation.

The LocalStorage Loophole

Trackers love LocalStorage because it never expires (unlike cookies).

• Facebook uses _fbp in cookies but also duplicates IDs in LocalStorage.
• Analytics tools often cache user events in IndexedDB to retry failed requests.

If a user clicks "Reject All," you must wipe all of this.

How GetCookies Handles "Deep Cleaning"

1. Auto-Detection

GetCookies doesn't just scan document.cookie. It wraps the window.localStorage and window.indexedDB APIs. We detect which keys are written by which scripts.

• Script: analytics.js -> Writes Key: user_session_v2

2. The "Nuke" Protocol

When a user withdraws consent, GetCookies executes a deep clean:

// Simplified Logic
if (consent_withdrawn) {
  // 1. Kill Cookies
  deleteCookie('_ga');
  
  // 2. Clear LocalStorage Keys mapped to Analytics
  localStorage.removeItem('mixpanel_distinct_id');
  localStorage.removeItem('hubspot_cart');
  
  // 3. Clear IndexedDB
  indexedDB.deleteDatabase('firebase_analytics_db');
}

Developer Best Practices

If you write your own code to LocalStorage:

1. Prefix your keys: Use marketing_ or necessary_.
   • necessary_theme_mode (Safe)
   • marketing_campaign_id (Requires Consent)
2. Listen for Events:

   window.addEventListener('getcookies:consent_updated', (e) => {
     if (!e.detail.marketing) {
       localStorage.removeItem('marketing_campaign_id');
     }
   });
   

Conclusion

A "Cookie" policy is insufficient in 2026. You need a Storage Policy. Ensure your CMP can reach into the browser's deeper storage layers to ensure a true opt-out.