Cookies & Browser Storage
Separate the browser’s saved clue from the service’s stored record.
Questions
Connected topics
Digital Advertising
A browser clue can help select an ad. Saving a shopping cart and choosing an ad are different uses of remembered information.
Digital Business Models
A remembered cart explains how a shop finds your items. To understand how a free service earns money, follow the separate business-model question.
Browser storage: mechanisms & limits
What does your browser remember—and where?
A website can save data in your browser and keep separate records on its servers. Cookies and Web Storage follow different rules.
Same browser. Different storage.
| Mechanism | Where | How it is used | Lifetime & limits |
|---|---|---|---|
| Cookie | Browser | Sent with eligible HTTP requests; scope and settings apply. | Expiry may be set, or session-based. Session restoration can matter. |
| localStorage | Browser / origin | Page scripts read or write it. Not automatically attached to requests. | Can persist across browser sessions; clearing, quotas and browser policies apply. |
| sessionStorage | Browser / origin and tab | Page scripts read or write it. Not automatically attached to requests. | Survives page reloads; tied to the page session, not a server login session. |
| Shop record | Service’s servers | The service looks up its own records. | Determined by the service; removing a browser item does not itself delete it. |
Technical references: MDN: cookies, MDN: Web Storage. Checked October 27, 2026.
Sources & further reading
- Google Ads — About dynamic remarketing
A provider’s technical description of past-visitor product ads; not independent evidence for a specific ad or a promised sales effect.
- MDN — Third-party cookies
First- and third-party context and storage behavior. Browser policies and settings matter.
- Google My Ad Center — How personalized ads work
Google’s stated personalization controls and non-personalized contexts; not every advertising provider’s policy.
- MDN — Using HTTP cookies
Cookies and eligible requests; persistence and session-restoration qualifications. The shop is an explicitly defined fictional model.
- MDN — Web Storage API
Browser storage types and scope; not evidence of a named shop’s implementation.
- MDN — Storage quotas and eviction criteria
Storage limits and possible deletion; no guarantee that local data lasts forever.
- OWASP — Session Management Cheat Sheet
Session lifecycle and explicit server-side invalidation. Recommendations do not establish that every service follows them.