Basic consent mode blocks every Google tag until a visitor accepts your banner, sending zero data before that moment. Advanced consent mode loads tags immediately in a cookieless "denied" state, sends anonymized pings, and models the conversions basic mode simply misses.
Below: what each mode does, a side-by-side comparison, and how the pings and modeling actually work. Then which mode fits your site and how to verify which one is running.
What Is Google Consent Mode?
Google Consent Mode is a framework that lets Google tags and SDKs adjust their behavior based on a visitor's cookie consent choice. A consent management platform (CMP) collects the choice through a banner. It then passes that choice to Google as one of four signals, so Analytics and Ads tags know what they can and cannot collect.
The four signals are:
ad_storage: controls advertising cookies and device identifiers.analytics_storage: controls analytics cookies, such as session length and visit counts.ad_user_data: controls whether user data can be sent to Google for advertising purposes.ad_personalization: controls whether that data can be used for personalized ads.
Consent Mode v1 used only ad_storage and analytics_storage. Version 2 kept both and added ad_user_data and ad_personalization, giving Google more detail on whether ad-related data can be sent and personalized. For the full model behind these signals, see Google Consent Mode.
What Is Basic Consent Mode?
Basic consent mode blocks every Google tag from firing until the visitor interacts with your consent banner. Before that interaction, Google's own documentation states plainly: no data is sent, not even the consent status itself.
Once the visitor accepts or rejects, the tags load and send their default consent state, then the updated state. Basic mode gives you the simplest privacy narrative: zero transmission until an explicit decision.
The tradeoff is on the reporting side. Nothing reaches Google before consent. So Google Ads and Analytics fall back on a general conversion model, not one built from your own site's pings. That fallback produces a wider gap between what your backend shows and what GA4 reports.
What Is Advanced Consent Mode?
Advanced consent mode loads Google tags immediately when a visitor opens your site, with default consent set to "denied" unless you configure otherwise. While consent stays denied, those tags send anonymized, cookieless pings, no cookies, no user identifiers, before the visitor has made any choice.
Once the visitor grants consent, full tracking activates. The cookieless pings collected during the denied period feed an advertiser-specific conversion model, more detailed than basic mode's general fallback.
In practice, advanced mode collects those cookieless pings from non-consented visitors and models the missing data from them. It only starts modeling once your site reaches Google's minimum traffic thresholds for that segment.
Basic vs Advanced Consent Mode: Side-by-Side Comparison
Basic and advanced consent mode diverge across six dimensions, from tag loading down to legal exposure. The table below compares both directly.
| Dimension | Basic Consent Mode | Advanced Consent Mode |
|---|---|---|
| Tag loading behavior | Tags blocked entirely until the visitor interacts with the banner | Tags load immediately with default consent set to "denied" |
| Cookieless pings before consent | None sent | Anonymized pings sent from the first pageview |
| Conversion modeling | General model, not advertiser-specific | Advertiser-specific model built from cookieless pings |
| Data completeness | Larger reporting gap when visitors decline or ignore the banner | Recovers more of the gap through modeling |
| Setup complexity | Simpler: block until consent, little else to configure | Requires correct default consent state and tag order in GTM, plus more testing |
| Privacy and legal exposure | Easiest "zero data before consent" narrative for an audit | Must document the cookieless-ping behavior in your privacy governance |
How Cookieless Pings and Conversion Modeling Work in Advanced Mode
While consent is denied, advanced mode sends anonymized cookieless pings: no cookies, no device identifiers. Those pings tell Google a visit happened without identifying who made it. Google combines them with the data it does collect from consenting visitors, then builds a model to estimate the conversions it cannot directly observe.
That model is an estimate, not a measurement. One e-commerce operator who enabled advanced mode saw GA4 report roughly £5.5k in conversion revenue against £17k in actual backend sales. Their cookie banner acceptance rate ran around 50 to 60 percent.
Modeled estimates are inherently less precise than direct cookie-based tracking. The modeled share of the data carries no user-specific identifiers to correct against. Expect a widening gap between GA4 and your backend numbers as your acceptance rate drops. That gap is not automatically a bug in your setup.
GA4's behavioral modeling has its own eligibility thresholds. Google needs a minimum volume of consented and non-consented traffic before it will model a given segment at all. A low-traffic site or a narrow segment may see little to no modeled recovery, even with advanced mode correctly configured.
Which Consent Mode Should You Use?
There is a definitive answer by site type, not a universal one. Google itself gives no recommendation, leaving the choice to "your company's guidelines". The decision comes down to two things: how much you rely on Google Ads, and how strict your privacy posture needs to be.
- E-commerce sites or anyone running Google Ads or Performance Max in the EEA or UK: use advanced mode. The modeled conversions it recovers protect your bidding accuracy directly, since basic mode's data gap causes Google's automated bidding to underbid on real demand.
- Low-paid-marketing content sites, blogs, or brochure and corporate sites: use basic mode. It is simpler to set up and sufficient when you do not depend on Google Ads conversion data for spending decisions.
- Regulated sectors (finance, healthcare) or a strict privacy posture: use basic mode. Its zero-transmission-before-consent narrative is the more defensible story in an audit.
Google expects at least basic Consent Mode v2 as a baseline for any site serving EEA or UK visitors through its advertising services. Advanced mode is optional on top of that. Skipping Consent Mode v2 where it applies costs you measurement and restricts remarketing features in your Google Ads account. So the baseline is not truly optional for EEA or UK advertisers.
Sites with no EEA or UK traffic are not required to run Consent Mode at all. Adopting it early still avoids a scramble if you later expand into those regions or start running EEA-targeted ads. Consent requirements also differ by region beyond Consent Mode itself; opt-in vs opt-out consent explains which model applies where you operate.
How to Check Which Consent Mode Is Running
Verify the mode by inspecting the consent parameters on the network request, or by reading Google's own platform diagnostics. The gcs parameter carries the ad_storage and analytics_storage state; the gcd parameter is always sent to Google regardless of consent mode. Four methods confirm which mode is live.
- Chrome DevTools Network tab (the practitioner method): open DevTools, go to the Network tab, and filter for "collect." Check the
gcsvalue on that collect request before you interact with the banner. Agcs=G100value before any interaction means advanced mode is active in a consent-pending state. - Interact with the banner, then check the collect request again: the parameter updating to
gcs=G111confirms full collection has started. If no collect request fires at all until after banner interaction, your site is running basic mode, not advanced. - Google Tag Assistant (Google's recommended method): open Tag Assistant, enter your site's URL, and step through the banner interaction. It confirms the four signals sit at "denied" before interaction and switch to "granted" after.
- Google Ads Diagnostics tab: in Google Ads, go to Goals, then Conversions, then Summary, select a conversion action, and open the Diagnostics tab. Google's verification guide shows it reporting either "consent mode is implemented" or "consent mode is implemented and modeling is active."
- GA4 Consent Overview: in Google Analytics, open Admin, then Data Streams, then Tag Settings, then Consent Overview to see which tags are using consent mode.
I have used the DevTools check to confirm a client's advanced-mode setup in under two minutes. No collect request before consent meant the tags were not loading pre-banner as advanced mode requires. That pointed straight to a default-consent misconfiguration in GTM, not a tracking bug.
Common Consent Mode Mistakes to Avoid
Most consent mode failures trace back to a handful of repeatable setup mistakes, not to the framework itself.
- Firing the consent-update tag after the purchase event: if the update fires after order confirmation, the purchase event can miss GA4 entirely. One practitioner described losing real conversions to exactly this race condition.
- Assuming advanced mode removes the need for a consent banner or CMP: both modes still require one. Consent mode adjusts what tags do with a choice; it does not replace consent management itself.
- Treating cookieless pings as automatically privacy-safe: they carry no cookies or identifiers. Document the behavior in your privacy governance rather than assume it needs no disclosure.
- Leaving default consent states unset: undefined defaults can let tags fire at full collection before any visitor makes a choice. That defeats the point of either mode.
- Never testing the setup in a real checkout or lead funnel: consent mode is technical enough that even experienced developers struggle with best practice. Test the actual purchase or conversion event, not just the banner interaction, before trusting the data.
How Consently Sets Up Google Consent Mode v2
Consently is a consent management platform that wires Google Consent Mode v2 automatically. You run either basic or advanced without hand-coding gtag('consent', ...) calls yourself.
Before any visitor interacts with your banner, Consently sets all four consent signals to denied by default: ad_storage, analytics_storage, ad_user_data, and ad_personalization. That privacy-by-default baseline is what advanced mode's cookieless-ping behavior depends on getting right.
Consently integrates with both gtag and Google Tag Manager. That keeps the consent update firing in the correct order relative to your other tags, instead of racing against them.
Once your banner records a choice, Consently sends the updated consent state to Google automatically, no manual tag-sequencing work on your end. See Consently's Google Consent Mode v2 feature for the full setup, or read how to set up Google Consent Mode v2 for the step-by-step version. Start free to wire Consent Mode v2 on your site.
FAQs
Is basic or advanced consent mode better?
Neither is universally better; it depends on your site. Advanced mode suits e-commerce and Google Ads-heavy sites that need modeled conversions, while basic mode suits low-ad-spend or strict-privacy sites that want the simpler setup.
Does basic consent mode send any data to Google?
No. Before the visitor consents, basic mode sends nothing to Google, not even the consent status itself, per Google's own documentation.
Is advanced consent mode GDPR compliant?
Yes, when configured correctly through a certified CMP. The cookieless pings carry no cookies or user identifiers. Still, document that ping behavior in your privacy governance instead of assuming it needs no disclosure.
Do I still need a cookie banner with advanced consent mode?
Yes. Both basic and advanced consent mode require a consent banner or CMP to capture the visitor's choice and pass it to Google. Neither mode replaces that step.
What is the difference between Consent Mode v1 and v2?
Version 2 keeps the two v1 signals, ad_storage and analytics_storage, and adds ad_user_data and ad_personalization. Those two additions give Google more detail on ad-related data sharing and personalization consent.
Is advanced consent mode the default in Google Tag Manager?
In some certified-CMP consent flows inside GTM, advanced is commonly the default implementation, but this varies by CMP. Verify your specific setup rather than assuming it.
Does advanced consent mode recover all lost conversions?
No. It recovers estimated, modeled conversions, not every real one. The model fills gaps in what it cannot observe; it does not measure the conversions it never saw.
Can I switch from basic to advanced consent mode later?
Yes. Switching is a configuration change in your CMP and tag setup, not a rebuild. Re-test your key conversion events after switching to confirm nothing broke in the process.
Do I need Google Consent Mode v2?
You need Consent Mode v2 if you serve ads to or measure EEA or UK visitors through Google's advertising services. Skipping it there costs measurement and restricts remarketing. Sites with no EEA or UK traffic are not required to run it.
How do I turn off Google consent mode?
You disable consent mode in your CMP or tag configuration, not in Google Analytics or Google Ads directly. Remove or switch off the consent-mode setup in your CMP, then re-test your tags to confirm they fire as expected.
