In this guide
- GA4 uses a client ID cookie (
_ga) to recognise visitors. With Consent Mode advanced, it sends cookieless pings when consent is denied. - Google then models the missing behaviour for properties that meet its data thresholds.
- A server container can set a first-party FPID cookie, and User-ID recognises logged-in users across sessions.
People ask whether GA4 can work "cookieless". The honest answer: GA4 is designed around a cookie, can adapt when the cookie is not allowed, and fills in some of the missing data with modelling. This page explains each mode and what it means for your reports. See Consent Mode v2, GA4 event tracking and cookieless tracking.
The normal case
With consent, GA4 sets cookies such as _ga and _ga_<ID> in the browser. The first holds a client ID that recognises a returning browser. The second keeps session data. With them GA4 builds sessions, users and paths.
Watch events arrive, live
A sample feed. In Open Tracked you see the same stream for your own store.
When consent is denied
| Mode | What happens | Reports |
|---|---|---|
| Basic Consent Mode | GA4 tags do not load until consent is given | No data from visitors who decline |
| Advanced Consent Mode | Tags load and send cookieless pings with no client ID when consent is denied | Google can model some of the missing behaviour, if thresholds are met |
| No Consent Mode | Tags fire, or do not fire, depending on your banner set-up | Gaps or compliance risk, depending on the set-up |
Modelling needs enough data: Google documents minimum volumes of events per day with analytics storage denied over a period, and of daily users with it granted. Small sites often do not qualify. See Consent Mode v2 for the thresholds.
Server-side options
FPID cookie
The GA4 client in a server container can set a first-party cookie in an HTTP response, which tends to last longer than a script-set cookie. See extending cookie lifetime.
User-ID
For logged-in visitors, send your own user ID. GA4 can then join sessions across devices. Use a non-personal ID, never an e-mail address.
Measurement Protocol
Send events straight from your server, for example purchases and refunds, with a client ID or user ID.
Cookie Keeper
Open Tracked can restore platform cookies for returning visitors who come back without them, with consent. It is on every plan.
Brands that grow on cleaner data
Stores and agencies use Open Tracked to see which ads earn the sale.
What you lose without cookies
- New versus returning becomes unreliable.
- Path and funnel analysis across sessions is weaker.
- Attribution loses the first touch for visitors who decline.
- Audience building for ads is limited.
A practical plan
Choose basic or advanced Consent Mode
With your advisor.
Send events to your own subdomain
And set the FPID cookie from the server.
Send User-ID for logged-in visitors
A non-personal ID.
Send purchases from the server
With a transaction ID.
Judge results with your store data
GA4 numbers for consenting visitors are a sample, not the total.
A realistic example
A store in Europe shows a consent banner, and about four in ten visitors decline analytics. With basic Consent Mode, GA4 sees only the six in ten who accept, and reports show about 6,000 sessions where the shop's own server logs show 10,000. After switching to advanced mode and sending events to its own subdomain, GA4 shows about 6,000 observed sessions plus modelled data in some reports, and the shop uses its own order data for the total. The shop stops expecting GA4 to match its logs, and treats GA4 as a sample of consenting visitors with a modelled uplift. That shift in expectation matters more than any setting, because it ends arguments about why the numbers differ.
Connected in minutes
Add your domain, install the pixel, connect your ad platforms and watch the first events land.
Frequently asked questions
Can GA4 work without cookies?
In advanced Consent Mode it sends cookieless pings, and Google may model missing data if thresholds are met. Reports are less complete than with cookies.
What is FPID?
A first-party client ID cookie set by the server container's GA4 client.
What is User-ID?
A non-personal ID you send for logged-in visitors, so GA4 can join their sessions across devices.
Does server-side tagging make GA4 cookieless?
No. It uses first-party cookies set by your server. Consent still applies.
How accurate is modelled data?
It is an estimate. Use your store numbers as the check.
Do I need spreadsheets to read my results?
No. Once tracking is live, the Open Tracked analytics shows spend, revenue, ROAS and profit, and you can ask Ari, the built-in AI assistant, questions about your own numbers in plain words. Ari's allowance depends on your analytics plan.
Is Open Tracked different from Open Track or Open Space Track?
No. Open Tracked is the official name of our server-side tracking platform, and the website is opentracked.io. Many people search for it as Open Track, OpenTrack or Open Space Track. All of them lead to the same product: server-side Google Tag Manager hosting, first-party analytics and a CRM pipeline.
Fix your tracking at the source
Open Tracked hosts your server-side Tag Manager, keeps first-party cookies alive and shows what each ad is really worth.
The Open Tracked team
We build Open Tracked: server-side tracking hosting, analytics and the tools around them, for stores that spend on ads. Questions about this guide, or an idea for the next one?
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