cookie-lifetime-audit

Auditing Cookie Lifetimes

Overview

Cookie lifetime is a critical compliance factor often overlooked in consent implementations. The CNIL recommends a maximum cookie lifetime of 13 months from the point of collection, after which consent must be renewed. The CJEU in Planet49 (Case C-673/17) established that cookie duration must be disclosed to users before consent is obtained. Additionally, browser-enforced restrictions — Safari's Intelligent Tracking Prevention (ITP), Firefox's Enhanced Tracking Protection (ETP), and Chrome's third-party cookie deprecation — impose technical limits on cookie lifetimes that may conflict with server-set durations. A cookie lifetime audit identifies cookies exceeding regulatory or technical limits and ensures accurate duration disclosure.

Cookie Duration Classification

Session vs. Persistent Cookies

Type	Duration	Behavior	Consent Implications
Session cookie	No `Expires` or `Max-Age` attribute	Deleted when browser closes	Still requires consent if non-essential under ePrivacy Art. 5(3)
Persistent cookie	Has `Expires` or `Max-Age`	Survives browser restart	Requires consent; duration must be disclosed (Planet49)
Server-refreshed	Reset on each visit via Set-Cookie	Effectively indefinite if user visits regularly	Duration is from last visit, not first set — must disclose rolling nature

Duration Categories

Category	Duration Range	Examples	Regulatory Concern
Short-lived	< 24 hours	Session IDs, CSRF tokens	Low — typically strictly necessary
Medium-lived	24 hours - 30 days	A/B test assignments, session replay	Medium — review necessity
Long-lived	30 days - 13 months	Analytics IDs, preference cookies	High — must justify duration
Excessive	> 13 months	Legacy tracking cookies, _ga (2 years)	Very high — CNIL non-compliant duration

CNIL 13-Month Recommendation

Regulatory Basis

CNIL's Recommendation on Cookies (1 October 2020, following Deliberation 2020-091 of 17 September 2020) states:

"The duration of validity of the consent of the user to the deposit of trackers should not exceed thirteen months. At the end of this period, the consent of the user should be collected again."

This 13-month maximum applies to:

The consent cookie itself (the cookie that records the user's consent choice)
Non-essential tracking cookies (the cookies enabled by consent)

Impact on Common Cookies

Cookies Exceeding CNIL 13-Month Limit:

Cookie	Default Duration	Set By	CNIL Compliant	Remediation
_ga	2 years (730 days)	Google Analytics	No — exceeds 13 months	Set `cookie_expires` to 34128000 (395 days / ~13 months)
_ga_XXXXXXX	2 years	GA4	No — exceeds 13 months	Set `cookie_expires` to 34128000
IDE	13 months	DoubleClick	Borderline compliant	Monitor — at the limit
fr	90 days	Meta/Facebook	Yes	No action needed
_gcl_au	90 days	Google Ads	Yes	No action needed
hjSessionUser*	1 year	Hotjar	Yes — under 13 months	No action needed
NID	6 months	Google Search	Yes	No action needed

GA4 Cookie Lifetime Configuration for Pinnacle E-Commerce Ltd

Override default GA4 cookie duration to comply with CNIL:

gtag.js implementation:

gtag('config', 'G-PINNACLE123', {
  'cookie_expires': 34128000,     // 395 days (~13 months) in seconds
  'cookie_update': true,           // Refresh cookie on each visit
  'cookie_domain': '.pinnacle-ecommerce.com',
  'cookie_flags': 'SameSite=Lax;Secure'
});

GTM implementation: In the GA4 Configuration tag, set the field:

Field name: cookie_expires
Value: 34128000

Browser-Enforced Lifetime Restrictions

Safari Intelligent Tracking Prevention (ITP)

Safari imposes strict cookie lifetime caps:

Cookie Type	ITP Rule	Effective Lifetime
Client-side JavaScript cookie (document.cookie)	Capped at 7 days	7 days maximum
Client-side JS cookie with link decoration (e.g., ?gclid=)	Capped at 24 hours	24 hours
Server-set cookie (Set-Cookie header), first-party	No cap	As set by server
Server-set cookie, classified as tracking	Capped at 7 days	7 days
Third-party cookie	Blocked entirely	0 (cannot be set)
LocalStorage	Capped at 7 days	7 days

Impact on Pinnacle E-Commerce Ltd:

GA4 _ga cookie set via JavaScript: Effective lifetime is 7 days on Safari, not 2 years
Server-side tagging (via data.pinnacle-ecommerce.com) sets _ga via Set-Cookie header: Full configured lifetime applies
Google Ads click IDs in URL parameters: _gcl_au cookie capped at 24 hours on Safari

Firefox Enhanced Tracking Protection (ETP)

Setting	Default (Standard)	Strict
Third-party tracking cookies	Blocked	Blocked
Cross-site tracking cookies	Blocked	Blocked
First-party tracking cookies	Allowed	Limited to 7 days (if tracker classified)
Fingerprinting scripts	Blocked	Blocked
Cryptomining scripts	Blocked	Blocked

Chrome Third-Party Cookie Changes

As of 2025, Chrome has moved toward a user-choice model for third-party cookies rather than full deprecation:

Phase	Status	Impact
Privacy Sandbox APIs available	Active	Topics API, Attribution Reporting API available
Third-party cookie user controls	Active	Users can block third-party cookies in settings
IP Protection (Gnatcatcher)	In development	May affect IP-based tracking