Why it happens
Shoppers who decline are no longer measured the old way. Consent Mode v2 passes four signals to Google tags: ad_storage and analytics_storage for cookies, ad_user_data for sending user data for advertising, and ad_personalization for personalised ads. When a shopper declines, Google tags stop using cookies for that purpose. Their purchases are no longer tied to an ad click in the usual way, so the count falls by roughly the share who decline.
Basic mode sends nothing before consent. In basic mode, Google tags do not load until the shopper answers the banner. If the shopper declines, no data goes to Google at all. In advanced mode, tags load at once and send cookieless pings while consent is denied, and Google uses them to model part of the missing conversions. Google says advanced mode gives an advertiser-specific model, and basic mode a general one.
Modeling is not active yet. Modeled conversions do not appear on day one. Google Ads applies an ad click threshold before it models conversions, which its help gives as 700 ad clicks over 7 days, or 100 a day, per country and domain grouping, and then adds them gradually to the Conversions column. GA4 behavioural modeling needs at least 1,000 events a day with analytics_storage denied for 7 days, and at least 1,000 daily users with it granted on 7 of the last 28 days. A small store may never reach these numbers.
The banner does not pass the answer on. On Shopify, a third-party banner must sync consent to Shopify through the Customer Privacy API. Shopify says that if it does not, your pixels might not fire even after a customer consents. Then shoppers who accepted are lost too. More in Shopify consent settings and missing purchases.
The banner shows in more regions than you meant. On new stores Shopify sets the cookie banner up automatically for visitors in the UK and the EEA. If it now shows everywhere, shoppers outside those regions decline too.
Check it yourself
- 1Find the day the banner or Consent Mode went live. Compare Google Ads conversions and GA4 purchases for the 7 full days before and after it with your paid online orders in Shopify admin for the same days.
- 2In Google Ads, open Goals > Conversions > Summary, choose your purchase action and open its Diagnostics tab. Google shows "Consent mode is implemented" or "Consent mode is implemented and modeling is active". The status can take 48 hours to appear, in some cases up to 2 weeks.
- 3In Google Tag Assistant, open your store, find the first Consent event and open its Consent tab. The On-page Default column should show Denied for a shopper who has not answered. Accept the banner and check that the latest Consent event shows Granted under On-page Update. For the setup itself, see Consent Mode v2 on Shopify.
- 4In GA4, open Admin, then under Data collection and modification click Consent settings. GA4 shows whether consent signals arrive for each data stream, for advertising and for analytics.
- 5In Shopify admin > Settings > Customer privacy, check in which regions the banner shows.
- 6In your consent tool, read the share of shoppers who declined since the change. A drop far larger than that points to a banner that does not sync to Shopify.
- 7Place two test orders in a private window: one after Decline and one after Accept. The accepted one must reach Google Ads and GA4.
What each platform needs with a purchase, consent included, is in how a paid order reaches Meta, GA4 and Google Ads.
FAQ
Is a drop after Consent Mode a bug?
Not by itself. Shoppers who decline are measured less, so the count falls. It is a problem when the drop is larger than your decline rate, or when shoppers who accepted are missing too.
Will the conversions come back?
Some may, as modeled conversions, once your account is eligible and modeling is active. Purchases from shoppers who declined do not come back as real conversions.
Should I switch to advanced mode?
Advanced mode loads Google tags before consent and sends cookieless pings. Whether that fits your markets is a legal decision for you as the store owner.