Key Takeaways
- The risk: A GA4 property created in just three clicks collects data—but that data is incomplete, not retained, and contaminated by your own traffic.
- Ten settings: property, traffic, tag, retention, internal traffic, enhanced measurement, key events, Google Signals, links, access.
- Duration: One hour for a showcase website; half a day for an e-commerce site with transaction tracking.
- Don't forget: Data retention for 14 months, set to 2 months by default.
Create a property Google Analytics 4 takes three minutes. Setting it up to produce reliable data takes an hour, provided you follow a specific sequence. The most costly errors (2-month retention period, internal traffic not excluded, missing conversions) only become apparent when you need the numbers—often months later. Here is the checklist we follow for every installation.
1. Create the property and the data flow
Since Administration > Create a Property, enter the name, time zone (Europe/Paris), and currency (EUR). These last two settings are often left at their U.S. default values, which shifts your days by 6 to 9 hours and skews your revenue. Next, create a “Web” feed using the website’s URL. Note the measurement ID (G-XXXXXXX).
2. Install the tag, preferably through Google Tag Manager
Three options: your CMS plugin (fast, but limited), the Google tag code pasted into the <head>, or Google Tag Manager. We recommend GTM whenever conversion tracking is planned: it allows you to add events without modifying the code and to manage consent. The guide GA4 and Google Tag Manager provides detailed installation instructions. Check the data reception in the Real-Time report.
3. Extend the data retention period to 14 months
Administration > Data Collection and Modification > Data Retention. The default value is 2 months: beyond that, your explorations can no longer be compared to the previous period. Select 14 months. Standard (aggregated) reports are not affected, but explorations, funnels, and segments are.
4. Exclude internal traffic and spam referrals
In the feed settings, Configure Tag Settings > Define Internal Traffic : Add the IP addresses of your offices and service providers, then enable the "Internal Traffic" filter in Data Filters (It is set up in test mode; be sure to switch it to production mode.) Also, add your payment providers (Stripe, PayPal) and your own domain to the list of excluded referrers; otherwise, every payment return will create a new session attributed to “paypal.com.”
5. Verify the improved measurement
Enabled by default, it tracks page views, scrolling, outbound clicks, internal searches, videos, downloads, and forms. Review each option: disable form tracking if your internal search engine triggers false positives form_submit, and check the internal search setting (often s or q). Details by event type is in our dedicated fact sheet.
6. Identify 3 to 5 key events
Without key events, GA4 only tracks traffic. Identify actions that drive business value (form submissions, calls, purchases, appointment bookings), create any missing events via GTM, and mark them as key events. Assign a value in euros—even if it’s just an estimate. For an e-commerce site, set up the events purchase, add_to_cart and begin_checkout (see GA4 and E-commerce).
7. Google Signals and Consent
Google Signals enhances demographic reports and enables cross-device remarketing, though it comes at the cost of lower display thresholds for smaller audiences. Enable it if you run Google Ads campaigns. In any case, in France, GA4 must be loaded only after consent has been obtained, with Consent Mode v2 configured. The requirements are detailed in GA4 and GDPR.
8. Link Google Ads, Search Console, and Merchant Center
Administration > Product Associations. The Google Ads integration imports your costs and allows you to send key events to the auctions (Connection Guide). The Search Console integration adds two reports on organic queries and pages, which you can then enable in the report library. Merchant Center is for stores that advertise on Google Shopping.
9. Manage Account Access and Ownership
The GA4 account must belong to the company—never to a service provider or an individual employee. Create at least two administrators using a company email address, assign agencies the “Editor” or “Analyst” role, and revoke their access once their assignments are complete. Review this list twice a year.
10. Document and monitor
Record the following in a shared document: tracking ID, tag location, list of events and their triggers, active filters, links, and people with access. Then schedule a review in 30 days: Are key events being tracked? Is internal traffic excluded? Do e-commerce revenues match those in your back office (a normal variance of 5% to 15% due to consent)? Our guide audit a GA4 account provides the complete procedure.
The Checklist at a Glance
| # | Adjustment | Where | Recommended value |
|---|---|---|---|
| 1 | Time Zone and Currency | Property Details | Europe/Paris, EUR |
| 2 | Tag | GTM or site code | GTM, verified in real time |
| 3 | Data Retention | Data Collection and Modification | 14 months |
| 4 | Internal traffic and referral sources excluded | Feed Settings, Data Filters | Office IP addresses, payment domains |
| 5 | Improved Measurement | Feed Settings | Enabled, options verified |
| 6 | Key Events | Events | 3 to 5, with value |
| 7 | Google Signals and Consent | Data Collection | As used in advertising, Consent Mode v2 |
| 8 | Connections | Product Combinations | Google Ads, Search Console |
| 9 | Access | Access Management | 2 company administrators, software development service providers |
| 10 | Documentation and Monitoring | Internal Document | 30-Day Follow-Up |
How GreenRed Can Help You
Instead of juggling multiple tools, the GreenRed Traffic module brings these metrics together in a single dashboard, compares them over time, and shows you which actions to prioritize. You can try it for free—no credit card required—on the page Rates.
Frequently Asked Questions
How long does it take to set up GA4 properly?
About an hour for a showcase website if you follow the checklist in order, half a day for an e-commerce site with transaction processing, and one to two days with a service provider for a complex website (multiple domains, an application, and an integrated CRM).
Should you use Google Tag Manager to set up GA4?
It is not required, but it is strongly recommended as soon as you plan to track conversions or manage consent. GTM allows you to add, test, and modify tags without modifying the website’s code, and to make their triggering contingent on the user’s consent.
Why don't my GA4 numbers match those from my store?
A discrepancy of 5 to 15% is normal: some visitors decline to give consent, certain ad blockers prevent the tag from working, and orders that are canceled or placed by phone do not appear in GA4. A larger discrepancy generally indicates that a “purchase” event was sent twice or is missing for certain payment methods.
What happens if the data retention period remains at 2 months?
Standard reports continue to work because they are based on aggregated tables. However, explorations (funnels, journeys, segments) and custom comparisons can no longer go back more than two months. Extending this to 14 months poses no drawbacks for an SME.